On-Board Diagnostics, A Heavy Duty Perspective · rods. Engines had rated horsepower occurring at 2100 rpm unless one was more fuel-efficiency conscious; then they could be ordered

SAE TECHNICAL PAPER SERIES

On-Board Diagnostics, A Heavy Duty Perspective

Mark R. Stepper Cummins Electronics Co., Inc.

Steven R. Butler Cummins Engine Co., Inc.

George G. Zhu Cummins Electonics Go., Inc.

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ABSTRACT

Malfunction detection and diagnostics for emission control systems have been incorporated by regulation into passenger cars, light duty trucks and medium duty vehicles. These systems, referred to as on-board diagnostics (OBD and OBD II), are intended to alert the vehicle operator of defective emission control devices so as to reduce the time between occurrence of the malfunction and its repair. The impact that detection and diagnostic systems have on the heavy duty engine and vehicle market will be explored by examining brief profiles and common practices of the heavy duty industry and vehicle customer.

DIAGNOSTIC REQUIREMENTS REGULATED by the California Air Resources Board (CARB) and the Environ- mental Protection Agency (EPA) will be discussed in this paper. This discussion will highlight the fact that diagnostic terminology, service publication, system monitoring, fault storing and indicator requirements have been defined. The regulated requirements will also be discussed to identify those that already apply to heavy duty vehicles. Inherent differences between light duty and heavy duty applications are leading the two industries to different diagnostic standards.

Heavy duty diagnostic standards have evolved because of the nonvertically integrated nature of the North American heavy duty engine and vehicle market. Engines in this market are certified on an engine dynamometer and then later installed by different vehicle assemblers into the truck chassis. In contrast, the typical passenger car and light duty truck manufacturer designs, builds and chassis-certifies the engines and the vehicle under the same manufacturing name.

On-Board Diagnostics, A Heavy Duty Perspective

Mark R. Stepper Cummins Electronics Co., Inc.

Steven R. Butler Cummins Engine Co., Inc.

George G. Zhu Cummins Electonics Co., Inc.

HEAVY DUTY MARKET OVERVIEW

Current and future applications of on-board malfunction detection and diagnostic systems in the heavy duty vehicle market afford the industry several opportunities. However, because the heavy duty vehiclelengine market is drastically different from the light duty truck and passenger car market, any new diagnostic system requirements must be integrated with existing systems and provide value to the end customer as well as a benefit to the environment. In order to better understand today's heavy duty on-highway industry, there is merit in looking at its history.

A HISTORICAL PEWPECTIVE - Several years ago, the customer of a heavy duty vehicle had many choices in his selection of engine and drivetrain technology. Engines could be chosen in either 2-cycle or 4-cycle, in-line 6 cylinders or V-8s, either indirect injection (IDI) or direct injection (DI). Some engines were offered with natural aspi- ration, some with turbocharging and some with super- charging. Soon water-to-air aftercooling started to appear. Timing of the injection events and fuel quantity were often mechanically controlled by use of camshaft lobes and push rods. Engines had rated horsepower occurring at 2100 rpm unless one was more fuel-efficiency conscious; then they could be ordered with a rating at 1800 or 1900 rpm. Vehicle drivetrains used transmissions that were typically of a gear- bound design, meaning that the top speed of the vehicle was obtained at the top speed of the engine. When reaching 2100 rpm, the vehicle reached 65 miles per hour. No higher road speed could be achieved.

The heavy duty vehicle averaged 3 to 4 miles per gallon fuel economy while traveling 100,000 miles per year. Engine rebuilds were done at 250,000 miles to replace worn-out parts and adjust major engine subsystems such as the fuel, lubri- cation and air handling systems. Repair typically involved removing and rebuilding entire systems as well as a11 power cylinder components.


Trucks occasionally incorporated only the bare necessities to allow the driver to do his job (i.e. a tachometer, a speedometer, an odometer and a fuel gauge). A tachograph was often used by the fleet owner to detect overspeed of the engine and drivers were paid on a per-mile basis.

TODAY'S CUSTOMER PROFILE - Today there is a much different picture of how goods are transported across our country. Due to emission regulations, the competition of engine manufacturers, and the desires and needs of the end customer, engine technology from all major engine su,ppliers has evolved to nearly the same level of sophistication. Engines today can typically be characterized by using such terms as 4-cycle, in-line 6 cylinders, turbocharged, air-to-air aftercooled with full authority electronics controlling such events as air-fuel ratio control and fuel injection quantity and timing. Gearing has changed to "gear fast, run slow" which makes the truck capable of running 80 miles per hour; however, a road speed governor limits the driver to legal limits, resulting in a slower running engine. This h~as all resulted in fuel mileage approaching 8 miles per gallon and improvements in durability so that engines are now lasting 600,000 miles or more before a major in-frame oveahaul. Electronics are now used to help determine which systems and power cylinder components are out of specification so that service can be done only on those parts needing repair, therefore avoiding excessive cost of repair, over-repair and extended equipment downtime.

Customers of heavy duty engines are extremely sensitive to the uptime of the vehicles in order to make their operations as profitable as possible. More uptime results in more product being shipped in a given amount of time. More product shipped results in larger revenue. One of the levers used to achieve more uptime is to encourage component suppliers to the heavy duty market to provide comprehensive diagnostics in order to keep the trucks rolling. Vehicles hauling precious commodities (e.g. food products) or transporting cargo clue in a specific time (e.g. just-in-time deliveries) cannot afford the financial loss resulting from downtime due to a lack of diagnostics.

Another significant factor in the heavy duty industry is the sensitivity to fuel economy. Most owners are concerned with fuel economy because of its direct impact on business profitability. It is also the view of many that if the fuel economy of the engine decreases it may be a sign of impending serious engine damage. For example, poor fuel economy can be the result of overfueling which in turn can result in damage to the engine. Poor fuel economy increases the operating costs of the business in two ways. First, the loss in efficiency due to poor fuel economy results in more dollars per mile to transport freight. Second, the life of the engine is decreased due to possible operation outside the design envelope, therefore decreasing the time to overhaul.

ELECTRONICS EVOLUTION - Vehicle electronics have evolved to the advantage of both the driver and the fleet owner. Features such as cruise control, idle speed aaljust- ment, engine power takeoff (PTO) operation and engine

protection systems all make the driver's job more pleasant. Today's vehicles are equipped with all the creature comforts most of us have come to expect in our passenger cars and then some-air conditioning, power steering, ergonomically designed seats, easy access to gauges and vehicle controls, and even sleeper compartments with microwaves and refrigerators.

Fleet owners have achieved control of operating expenses by being able to limit vehicle speed, shorten idle time and schedule preventive maintenance. Additionally, the heavy duty trucking industry has been incorporating on-board satellite linkups to allow the driver to maintain communication with the freight terminal. These on-board computing devices can provide engine status, geographic position reporting, and connection to the dispatcher, the shipper and emergency services; any party involved in the moving of a particular load of freight is instantly aware of any aspect of the move. Reported cases of communications between a vehicle and its dispatcher have allowed on-the-road diagnosis and subsequent repair to occur before the vehicle had a mission-disabling failure. Therefore, faster diagnosis and repair have helped to improve the vehicle uptime.

Along with this increased use of electronics to control engine and vehicle functions came the ability to incorporate malfunction detection and diagnostic measurement, usually at minimal cost. In fact, most heavy duty electronic engine control systems in use today require real time monitoring of such parameters as intake manifold temperature, turbocharger boost pressure, air-fuel ratio control, injector solenoid parameters, oil temperature and pressure, coolant temperature, coolant level, fuel consumption and hours of operation to name a few. Many of these monitoring operations are incorporated to allow the envelope of the engine design to be pushed to its current limits. Both engine fuel economy and horsepower have increased simultaneously due to the customer's demand for both. Electronics and the diagnostic opportunities they make possible are allowing this increase in horsepower to engine weight. The diagnostic monitoring is a requirement to make sure the engine operates within its design envelope even during powertrain system anomalies. As the vast majority of emission reductions occur in the cylinder, one could assert that the heavy duty engine industry is already performing emission malfunction detection and diagnosis without the need of regulatory rules to drive it.

Customers have come to expect this advancement of technology; to offer anything less is not acceptable in today's market.

CHARACTERISTICS OF THE HEAVY DUTY INDUSTRY - When one thinks about the application of on- board diagnostics to heavy duty vehicles, one must acknowledge several distinct differences within the heavy duty vehicle industry in the United States. Differences in the areas of corporate integration, production volumes and engine certification must all be taken into account before any type of requirement for regulated on-board diagnostics can be considered.


The heavy duty vehicle industry infrastructure differs from the U.S. passenger carnight duty truck industry as well as the European passenger car and heavy duty truck industry. The U.S. heavy duty truck industry is nonvertically integrated, meaning the heavy duty truck assemblers do not typically manufacture the engines used in the vehicle nor other components such as brakes, axles or transmissions. The end customer of a US.-built heavy duty truck has a choice of engine manufacturers such as Cummins, Caterpillar or Detroit Diesel; a choice of transmission manufacturers such as Rockwell, Eaton, Spicer or Allison; and a choice of axle manufacturers such as Rockwell or Eaton. This allows the end customer to select specific components that will best accommodate the operation and mission of the vehicle he wishes to purchase. In the U.S. passenger car market as well as the European passenger car and heavy duty truck market the vehicle assembler is usually the same entity that designs and builds the engine, transmission and other driveline components. Examples of these manufacturers in the United States are Chrysler, Ford and General Motors. European vehicle manufacturers such as Volvo, Scania and Mercedes Benz also build complete vehicles.

The U.S. heavy duty vehicle industry has a much lower production volume when compared to the U.S. passenger car industry. In 1994, United States and Canadian heavy duty (Class 8) vehicle production was approximately 207,000 units while passenger cars totaled nearly 12 million.

Another key difference with the heavy duty vehicle is the method in which the engine is certified for exhaust emissions. In the passenger car market, the engine is installed into the vehicle and then the entire vehicle is tested for exhaust emissions on a chassis dynamometer with emissions measured in grams of pollutant per mile driven. The heavy duty engine on the other hand is tested on an engine dynamometer and emissions are measured in grams of pollutant per unit of work (horsepower-hours). This recog- nizes that heavy duty engines are used on a commercial basis and that their value in doing work is more valuable than simply the miles driven (e.g. one large truck is more efficient and less polluting than several smaller vehicles transporting the same amount of product).

The U.S. heavy duty vehicle market is a very competitive one. Engine manufacturers as well as other driveline component manufacturers and vehicle assemblers are advancing technology in an effort to satisfy customer needs. Fuel economy, durability, reliability, driver comforts and the overall cost of operation (life cycle cost) are all attributes that can set apart one product from another. Because of this, the advancement of electronic features and systems has accelerated quickly over the last several years. This has been driven largely by customer demand, not by regulatory action.

HEAVY DUTY INDUSTRY APPROACH TO ON-BOARD DIAGNOSTICS

Heavy duty diagnostics began to be standardized in the mid-1980s. Early influences on standardization were (a) truck original equipment manufacturer (OEM) demands due to their nonvertically integrated nature; (b) the need for component suppliers to have ways to connect to their component for diagnosis; (c) pressure from large fleets which would have to service and repair these vehicles; (d) desire by most industry players to avoid reengineering each combination of components on a vehicle. And finally, what is arguably the most powerful reason (e) the desire to have strong acceptance of electronics by end users. These early influences of on-board diagnostics resulted in SAE Truck and Bus (T&B) recommended practices such as 51708, 51587, 51922 and 51924, as well as the American Trucking Association's (ATA) The Maintenance Council's (TMC) RP- 1202.

It is important to note that these standards were not driven from an emissions regulation standpoint. These standards were the result of a nonvertically integrated industry desiring a way to work together more effectively to supply products that could be integrated easily without having to redesign for each heavy duty truck OEM's specific application or unique combination of components.

There was also a strong desire to have industry standard service tools that could diagnose the on-board electronics. As it has evolved today, many of the major electronically controlled devices (engines, transmissions, traction control systems, etc.) have required vehicle dash lamps to relay error conditions to the vehicle operator. Some engine systems, for instance, require as many as three lamps (warning, stop and protect lamps). Many of the component suppliers use these lamps during normal vehicle operation to communicate to the driver that a fault condition exists that could warrant stopping the operation of the vehicle. Many of the component suppliers also used their lamps to flash out proprietary blink codes that could then be used to help determine the reason for the fault condition. With the availability of electronics and the use of microprocessor-controlled displays, it is expected that these blink codes will disappear in favor of alphanumeric displays which are addressable over industry standard data links.

While some reported faults could probably be catego- rized as emissions related, heavy duty component suppliers do not categorize faults as related or not related to emissions. The goal was to provide the standardized fault code information needed to fix a fault condition and it was not important whether that item was emissions related or not. The standardized fault code currently uses a strategy that defines the source of the fault as the sender of the message on the data link (e.g. engine), the failure mode (e.g. open circuit), the least repairable component (e.g. engine oil pressure circuit) and optionally the number of times the fault has gone from active to inactive (occurrence count).


HEAVY DUTY DIAGNOSTICS AND DATA LINKS amount of commonality among OBD 11, KWP 2000 and SAE IN TUNSITION - The second generation heavy duty J1939J73. diagnostics approach has tried to take into account many factors. Three important factors have been the desire: to (1) improve the first generation of heavy duty diagnostics; (2) satisfy OBD I1 goals; and (3) provide the diagnostic services that are being identified in International Organization of Standards (ISO) Keyword Protocol (KWP) 2000. KWP 2000 documents identify diagnostic systems as physical layer, data link layer and application layer. There is a sigriificant

The second generation heavy duty diagnostics define a fault code as a diagnostic trouble code (DTC). This definition can be found in 51939173. The DTC continues with a strategy similar to today's but has allowed for more failure modes to be defined (a total of 32), more available least- repairable component identifications (about 500,000) and fewer occurrence counts (1 27). See Figure 1.

A. DTC Definition

1 19bits 1 5bits 1 lbit 7 bits

4 Byte Value Quals I>TC

Suspect Parameter Number (SPN)

B. Examples

Example 1

SPN = 91 Suspect pardmeter is accelerator pedal position. - It is assigned the same number as the PID for this parameter in 51587,

FMI = 3 Failure mode is identified as voltage above normal. OC = 5 Occurrence count indicates trouble has occurred 5 times.

Example 2

SPN = 662 Suspect parimeter is engine injector number 12. - This is not a parameter communicated on 51587. - Therefore it is assigned a number above 5 1 1.

FMI = 3 Failure mode is identified as voltage above normal. OC = 2 Occurrence count indicates trouble has occurred 2 times.

FIGURE 1: Example of Second Generation Heavy Duty Diagnostic Trouble Code

Failure Mode Identifier

(FMI)

One of the differences with the second generation heavy duty diagnostics is that the diagnostic trouble code identifies a failure the same way whether the parameter is communicated on the vehicle network or not. 51587 on the other hand used parameter identifiers (PIDs) for parameters communicated on the network and subsystem identifiers (SIDs) for nonnetwork parameters. For both the first and second generation heavy duty diagnostics, determination of the location and type of controller on the vehicle that detected the fault is acquired with a query to that device on the network.

As with today's heavy duty diagnostics, a new parameter assignment automatically results in that parameter being diagnosable. The new parameter is assigned a Suspect Parameter Number (SPN). These assignments are in the J1939 top level document. When new parameter assignments are made, they will follow the J1930HD Terms, Definitions and Acronyms naming requirements. Following these naming requirements will result in a consistent and easy-to- use set of parametersJterms.

Heavy duty products have used the industry standard serial communication networks for many functions. One practice is to program customer feature settings at the point of original vehicle assembly or while servicing the product. An example of a customer feature setting would be where one truck OEM wants the cruise set switch to cause an acceleration after a predetermined time and another truck OEM wants the cruise set switch to cause a deceleration. Serial commullication networks have also been used by some manufacturers to program data and to program executable code. Data include engine fuel and timing maps while executable code can be corrections to previously released software capabilities or it can include the addition of new executable code for a new feature added to an electronic control module. To date, each component supplier has incorporated its own security schemes to prevent tampering with data andlor code.

Reserved for SAE

Assignment

Occurrence Count (oc)


SERVICE INTERFACE - The diagnostic service tools of the heavy duty industry are used to recover the faults detected by the electronic control module while more sophisticated tools can run specific diagnostic tests designed to diagnose engine performance, perform engine dynamometer setups, and collect and maintain service data bases on trip functions, diagnostics, etc. There are three basic levels of the heavy duty diagnosis: (1) fault lamps, (2) handheld diagnostic service tools, and (3) proprietary, custom-designed, full-function portable tools which are now being replaced by personal computer (PC) Windows-based diagnostics service tools.

The fault lamps are used during normal vehicle operation to alert the driver that a fault condition is being encountered. During a diagnostic session, they can also be used to provide the fault code in the form of a blink code so service personnel can check the manual to determine the possible cause of the fault and fix the fault condition.

The handheld diagnostic service too1 communicates with the electronic control module through the SAE standard serial data link to read fault codes and other service data. In addition, some handheld service tools are able to change the customer-adjustable parameters and perform diagnostic tests and setups.

The PC Windows-based service tool, the latest engine diagnostic service tool, provides not only all handheld service tool functionalities but also many new features that become available with the computing resources of a PC. With large quantities of random access memory (RAM) and disk space available, there is a great capacity for data collection and manipulation. The organization and presentation of the data can also be optimized for the larger display that is available with the PC. Another very attractive feature is that one PC can operate the software necessary to service many different heavy duty vehicle components.

REGULATED DIAGNOSTIC REQUIREMENTS

The current requirements for on-board diagnostics as regulated at the federal level by the EPA cover only vehicle applications up to 8500 pounds gross vehicle weight rating

(GVWR). Manufacturers of heavy duty engines are therefore not required to design and develop OBD systems for vehicles in the 49-state federal market. However, the California Air Resources Board in 1989 created a unique vehicle classification titled Medium Duty Vehicles which covers vehicles ranging from 6,000 to 14,000 pounds GVWR. This new classification became effective in 1995. Both chassis- dynamometer and engine-dynamometer certified engines participate in this classification. See Figure 2.

Therefore, several engine manufacturers producing heavy duty engines for vehicles above 8500 pounds GVWR for the 49-state market are covered in the Medium Duty Vehicle classification range in California. The most obvious example of these products is the upper end of the pickup truck market using either diesel or larger gasoline engines. Manu- facturers must therefore produce engines compliant with the California Malfunction and Diagnostic System Requirement for 1994 and Subsequent Model Year Passenger Cars, Light Duty Trucks and Medium Duty Vehicles and Engines commonly called OBD I1 (reference Title 13 Section 1968.1 of the California Code of Regulations).

Included in the OBD 11 regulation are the following SAE Motor Vehicle Council (MVC), SAE Truck and Bus Council and International Organization of Standards recommended practices.

SAE MVC

51 850 51962 51979 51978 51930 52012

SAE T&B

51939 J1939101 51939111 51939121 51939131 51939171 51 939173 5193918 1

IS0

IS0 9141-2 KWF' 2000

(1 to 3)


GVWR (pounds):

0-------6000-.------ 8500-----.---10000--------- 14000---------16000------.--- 19500 ---- --- .,--- ---26000---------------- 33000------ 3

EPA Classification:

CARB Classification:

_Certification Method:

-- Pass Medlud Dwty VeKwb car

FIGURE 2: Vehicle Class=cations

Heavy Duty Vehicl.esmgbes

Vehicle Class:

OBD I1 MONITORING REQUIREMENTS - 'OBD II has created definitions intended to identify the systems on a vehicle that need monitoring. These are mostly emission- related systems and therefore many are powertrain related. OBD I1 has ten major monitoring requirements: nine spexific monitors and one catchall. The nine monitors are (1) catalyst, (2) heated catalyst, (3) misfire, (4) evaporative system, (5) secondary air system, (6) air conditioning system refrigerant, (7) fuel system, (8) oxygen sensor, and (9) exhaust gas recirculation (EGR) system.

-

The catchall category (10) is called comprehensive component, which basically requires most inputs and outputs to be tested for circuit continuity and proper response. Additionally, there are special tests called rationality tests that suppliers must verify that a measured signal is reasonable when compared to other measured data available to the electronic control module. Any component that directly or indirectly affects emissions is required to be monitored under the comprehensive component section. Any signal that may enable or disable any monitor is defined as indirectly

8

affecting emissions, including sensors that may be used to improve the reliability of diagnostic monitors.

The nine monitors are intended to verify the specific system is performing its prescribed function for the useful life of the vehicle. These monitors are required, in most cases, to light the malfunction indicator lamp (MIL) when they detect a condition that causes emissions to go beyond 1.5 times the regulated emission limits. Many of these monitors must confirm that the physical operation is being performed. An example would be to assure the correct amount of exhaust gas is flowing through the EGR system under appropriate test conditions (e.g. confirm that neither too low nor too high a flow is occurring).

6 3 1

Current designs of electronically controlled heavy duty diesel engines do not use many of the nine systems which require monitoring under existing OBD I1 rules. Three-way catalysts, heated catalysts, secondary air and EGR are not now a part of the designs. Current systems are doing an adequate job of assuring proper operation of the electronic

7 2a 2b


controls over the life of the vehicle. For example, some heavy Table 1 describes the applicable CARB OBD I1 require- duty suppliers add capabilities to their control modules to ments for various types of engines. The term Not applicable detect rationality-type failures of signals such as the intake air means a particular system is not used by that engine type pressure sensor which is used to help assure the engine and/or its monitor is not required by law. No means the system is operating at a proper air-to-fuel mixture. This type technology for performing the monitor function has not been of monitoring also can detect attempts to tamper with determined and may not be feasible at a sensible cost until emission-related fuel limits. technology breakthroughs occur.

TABLE 1: OBD I1 Compatibility Matrix

REGULATED DIAGNOSTIC FEATURES - Table requirements, not as OBD 11. Therefore when asked, "When 2 contains a comparison of SAE MVC, SAE T&B and IS0 do you think OBD I1 will be required on heavy duty recommended practices that are regulated as part of OBD, vehicles?' the answer is not straight forward. It appears that OBD I1 and the European Union OBD rule that is under OBD I1 requirements are being phased in on the heavy duty development. Some of the SAE standards required by OBD vehicle industry. or OBD I1 for medium duty vehicles and passenger cars have been required of the heavy duty vehicle industry as separate

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.:;,;:;. ............................. ..:.::::::: ..............".... .......................... ...............A"........

;iPj.@Ii3ig:z &-m .......................................... ........................................... ............................................. i f i~e ~:.~~"..:':.:,:.:..~>.:.~::?".:-

:.i:::::i:$::::::::,; [;;$a$#&&i@&@@2: :::i:::>::.:.::::::::,:,: .,.,:,: ,:::.:.: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . :\ .................................. ....................

Catalyst1

Heated Catalyst

isf fire' Evaporative System1

Secondary Air System

Air Conditioning System Refrigerant

Fuel System

Oxygen Sensor

EGR System

Comprehensive Component .:....... .,:.... .... .............................................. . . . . . . . . .....;.: ............................... ,:,::.:5:::.; ,,,,; ........................... ......... ...'.. :'::' ............. :.:.:.:.:..,:.:.:., . . . . . . . . . . . . . . . . . . . . . . .

Model Year for Compliance

Intermediate requirements exist until 1997 model year. Diesel engines are required to monitor misfire for the 1998 model year. A one-year exemption is available with CARB executive officer approval. Special concessions are allowed until the 1999 model year on monitors made impractical due to use of alternative fuel.

Yes, if stoichiometric

Yes

Yes

Yes

Yes

Not applicable, if non-CFC

Yes

Yes

Yes

Yes ................... .................................... .... '.....'. ::::.::fi .:.:.. ,:.:.:::: p-pp ................. : ................................

1994

No

No

yes2

Not applicable

Not applicable


Yes

No (not used)

Yes

Yes ...... :':';: :':'.':':'.' ."'"'.'."'~""

...................................................................................................

1 9963

No, if lean burn Yes, otherwise

No, if lean bum Yes, otherwise

Yes

Not applicable

Not applicable


Yes

Yes

Yes

Yes ................................. ............. ..:,:,:.:.:.: :.:..... ............-.. . . . . . . . . . . . . . . . . . . . . . . . . ... : ........... ...

1 9964


TABLE 2: Itegulatory Agency Requirements

Diagnostic Features

Monitoring Algorithms and Lamps

EPA (OBD) Car and Light Duty Truck

Connector

EPA (OBD)

Data Link: Electrical, Message Formatting, Addressing

(OBD Light Duty

Truck and Medium Dutv Vehicle

51962

Terms/Definitions/ Acronyms

(OBD

11850, I S 0 9141-2

Service ToolsIScan Tools

European Union Car and Light Duty

Truck1

51 962, 9193g2

51930

Diagnostic Services and Freeze Frame

Diagnostic Trouble 1 J2012 1 None 1 Kw 2ooo9 part 1 None 1 Codes

J2012, J 1 9392 -- (5201 2)

Security 52 1 86 (remanded) KWP2ooo,part3 J21863

-- (52 1 86)

EPA, CARB nod European Heavy

Duty Vehicles

European Union rule similar to OBD 11

51850, IS0 9141-2, J19392

51978

51979 KWP 2000, parts 2 and 3 (superset of 519791

None

KWP 2000, Part 1 (51962)

51930

None

Planned for approximately the year 2000 I

N~~~

KWP 2000, part 1 (IS0 914 1-2)

51978

Service Documentation Format

Optional for CARB medium duty vehicles I

None

KWP 2000 (11930)

Only required by CARB to prevent tampering with calibrations or adjustable parameters: Mail Out #94-16, dated 313 1/94 I

51 930 (Under revision for heavy duty

KWP 2000, p a s 2 and 3 (J1978)

~ ~ ~ 0 8 4

Planned as part of OBD but recommended practice not completed in time for inclusion in OBD rule - I

N~~~

EUROPEAN DIAGNOSTICS DEVELOPMENT - APPLICATION OF ON-BOARD DIAGNOSTICS TO The European Union is drafting laws that will establish HEAVY DUTY ENGINES similar requirements as OBD I1 and OBD have in the United States. It is thought that these new rules will allow vehicles As the heavy duty diesel engine control systems have with CARB OBD I1 or EPA OBD certified systems to operate moved from mechanicaVhydraulic toward electronic controls, in Europe. The new European Union OBD is expected to engine diagnostic capabilities were added. They are contin- reference the KWP 2000 documents. This three-part docu- ually being improved and are one of the most important ment, IS0 14230 (-1, -2 and -3), is a superset of those requirements for the engine control system.

:None

diagnostic functions needed to comply with OBD 11 and Diagnostic fen?-~r:s are defined to make electronic - OBD. The superset of diagnostic services that are defined is troubleshooting accu IL-, easy and fast. The current heavy

similar to those defined in SAE MVC 52190. A more general duty diagnostics cort 112 many features which seem to meet diagnostic services strategy is discussed in IS0 14229 and is the intent of OBD 11 . qlrrements and may in some cases go meant to be independent of the serial communications beyond them. P. ccn pinson of heavy duty and light duty physical or data link layer used. The diagnostic service industry standards 1 , I ,>ed in Table 3. definitions of IS0 14229 are similar to those defined in IS0 14230 part 3 and SAE J2 190.

None None


TABLE 3: Diagnostic Features and Recommended Practices

DIAGNOSTIC SYSTEM DEFINITION - In general, heavy duty diagnostic systems can be divided into four groups: (1) error detection, (2) error processing, (3) service interfaces and (4) service tools. Figure 3 shows a graphic illustration of the four diagnostic groups in detail; the dashed line boxes distinguish the on-board from the off-board diagnostics. The on-board diagnostics are accomplished in real time by electronic control modules permanently installed on the vehicle while the off-board diagnostics are accomplished by using a service tool connected to the electronic control modules through a data link.

Diagnostic Features and Serial Communications

1. Monitoring Algorithms

2. Diagnostic Trouble Code

3. Freeze Frame

4. Monitored Parameters

5. Lamps

6. Message Formatting

7. Electrical

8. Connector

9. Addressing

10. Terms/Definitions/Acronyms

11. Service ToolslScan Tools

12. Diagnostic Services

13. Service Documentation Format

14. Security

15. Vehicle Electronics Programming Stations (VEPS)

16. Controls (e.g. powertrain)

17. Information Sharing

' OBD I1 regulates all light duty

Figure 3 identifies those capabilities defined by this paper as making up a vehicle diagnostic system. The error detection box represents strategies incorporated into an electronic control module to determine when a possible error condition exists. The monitoring algorithms determine open or short circuits, rationality error conditions, and end-to-end subsystem functionality errors. The next box, error processing, includes operations that occur once the error

condition has been determined and the electronic control module wants to make a record of the event and take action. This might include saving the freeze frame (e.g. the time, engine rpm, mph, engine load and occurrence count when the error occurred), changing the state of the indicator lamps and possibly putting in place some protection scheme that might limit engine power.

duty in this table. Under development by the ATA TMC Study Group 5 subgroup named Establishing a Standard for the Exchange of Electronic Service Information.

Industry Light

Light ~ u t y l

OBD I1

520 12

51979, OBD I1

J219O,J1979,J2178/2

51979 (MIL only), OBD I1

51979,J2190,J2178/1

51850, IS0 9141-2

J1962

J2190' J2178119 J217813' 52 17814

J1930

J2205, J2201, J1978

J1979,52190, J2205

J2008

J2186, OBD 11, OBD

Proprietary

Proprietary

521 7812

(LD) and medium duty (MD)

The third box, service interfaces, identifies characteristics that allow a consistent interface to off-board service tools and personnel. This covers such items as data link requirements for electrical characteristics, message formatting, electronic control module address assignments and data scaling. Data link connector dimensions and pin assignments are specified. The terms, definitions and acronyms are specified so that the person doing the service does not have to struggle with the use of different technical terms to identify the item or subsystem to be diagnosed. Also included in this area is the use of the indicator lamps to identify specific

Duty and Heavy Duty

HD (Current) First Generation

Proprietary

51587

NIA

J1587

J1587

J1708,51587

J 1708

RP- 1 202

J1587, J1708, J1922

J1930 (Guide)

RP- 1202

J1587

Proprietary

Proprietary

J1924,J2214

J 1922

J1587

applications. Medium duty

Recommended Practices

HD (Future) Second Generation

Proprietary

51939173, J1939

51939173

J1939M1, J1939

J1939173

51939121, J1939173, J1939171

5193911 1

5193911 1,51939173

J1939/31,J1939/81, J1939121

J193OHD

TBD

51939173

ATA TMc2

J1939173

TBD

51939171

J1939/71

is also a subgroup of heavy


diagnostic trouble codes by blinking them in a predefined manner (blink codes).

The last box, service tools, represents those functions expected to be provided by the off-board service tool (e.g. diagnostic information processing, troubleshooting proce- dures, diagnostic services activation, etc.). Also included is the service documentation which assures that the necessary information to troubleshoot and repair vehicles is available in a consistent format and structure.

the first in the list. Customers of heavy duty vehicles expect a high percentage of vehicle uptime and demand resolution of conditions which negatively affect fuel economy. Most often, the heavy duty vehicles are owned by independently operated fleets. In their own interests, fleet managers also require on- board diagnostic systems to be able to detect not only the subsystem defects due to failures but also vehicle tampering such as disconnecting the vehicle speed sensor to achieve higher vehicle speeds, adjusting intake manifold pressure readings in an attempt to disable air-to-fuel ratio control.

The ellipse at the bottom represents those entities that influence each of the four boxes. Notice that the customer is

FIGURE 3: Definition of System Diagnostics I

DIAGNOSTIC COMPARISONS - Many heavy duty success of the repair before the trouble code is made inactive diagnostic features are quite different from the light duty and allowed to be cleared. ones. The following are a few examples to compare heavy duty and light duty diagnostics. Some heavy duty diagnostics monitor and report whether a fault is considered active or previously active and only allow clearing of previously active faults by the service technician. OBD 11 recommends keeping track of active faults and allows them to be cleared by the service technician. However, with OBD I1 a separate indicator is provided which tells the service technician when the monitor has run so the repair can be verified. These separate indicators are named readiness/fnction codes by OBD 11. Both systems achieve the same end result with one noted difference. The OBD I1 approach makes it possible: for an active fault to be cleared, leading the customer to believe the repair was successful only to find out one or more driving cycles later that the fault becomes active again. The motivation for the heavy duty approach has been that the electronic control module should be the device that tests the

For heavy duty applications, as long as a fault is active, an engine warning lamp will be illuminated. The OBD 11 regulation allows the malfunction indicator lamp to be turned on during the second driving cycle in which the fault occurs for many of its monitors. Another difference is that the heavy duty diagnostic system uses the fault occurrence count to record how many times a fault has gone from active to inactive, which helps service personnel troubleshoot intermittent faults. The OBD I1 regulation has no such allowance. In addition, some heavy duty suppliers provide for multiple freeze frame records (e.g. 16 to 32 faults) while OBD I1 only requires one freeze frame. The heavy duty service and control data link interfaces are controlled by the SAE Truck and Bus Council recommended practices and ATA TMC recommended practices. In the light duty case, OBD I1 service interfaces are controlled by SAE Motor Vehicle Council recommended practices. The recently de- veloped SAE 51939 recommended practices are in the process

10


of replacing those currently used to standardize the service and control interfaces. Note that SAE 51939 has been recently recognized as an option for those applications required to meet OBD I1 regulation.

For heavy duty, medium duty and light duty vehicles, the service tools can be divided into two categories: industry- standard service tool and OEM-specific service tool. The industry-standard service tools contain the basic service

features defined in SAE standards, and the OEM tools contain many features that standard service tools do not have.

Figure 4 illustrates the application of heavy duty industry recommended practices for diagnostics and serial communications. This figure identifies both the new heavy duty industry recommended practices (the SAE 51939 series) that apply to specific functions in system diagnostics discussed in Figure 3 and the light duty recommended practices which are identified in brackets.

FIGURE 4: Application of Diagnostic and Communication Recommended Practices

Industry and customer requirements have led to the development of many SAE and ATA TMC recommended practices in the heavy duty industry. When comparing the heavy duty recommended practices to those available in SAE Motor Vehicle Council prior to government regulation, it is clear the markets are much different and the need for voluntary industry standards is much greater in the heavy duty industry. To alleviate the need to develop custom hard- ware and software for each vehicle OEM, the heavy duty industry component suppliers required industry standards to be available whereas for the typical passenger car OEM the incentive to use industry standards is less because the vehicle components are mostly passenger car OEM supplied and integrated. Also, the service of these vehicles is done by OEM-specific locations that use proprietary tools to perform

the diagnosis. Granted, many of the independent service locations are definitely in support of a common service tool approach. The benefit of standardization for the vehicle OEM is not as apparent as it is for the heavy duty industry component suppliers. There is less need for industry standard interfaces for components when the vehicle OEM is vertically integrated.

The heavy duty industry has been able to achieve a level of standardization which assures, for instance, that any 51708 device can connect and communicate with another 51708 device. This is the same with 51939/01 for heavy duty vehicles. Some of the SAE Motor Vehicle Council specifications for light duty tend to allow for multiple definitions and/or proprietary definitions. This means in many cases there is no


, confidence that if one connects two devices they will communicate.

Table 3 illustrates the point that heavy duty industry has achieved industry standardization in the areas of diagnostics, control, vehicle electronic programming stations and vehicle information sharing via data links.

REGULATION CONCERNS - If any regulatory agency were to consider the regulation of on-board diagnostic systems for heavy duty engineslvehicles, several issues unique to the heavy duty engine certification process and the !heavy duty enginelvehicle industry would need to be addressed.

The first issue is the fact that the heavy duty engine is certified on an engine dynamometer following a federal test procedure (FTP) which is a transient test cycle designed to simulate city and urban operation. This cycle is comprisecl of one cold cycle (+25 OC [+77 OF] ambient temperature) and one hot cycle (normal engine operating temperature). When calculating the final emissions value, the hot cycle is given a weighting factor six times that of the cold cycle. The rationale for this weighted emphasis on the hot cycle is that heavy duty engines are mainly used in commercial or more continuous-usage applications which tend to have a lower ratio of cold-start driving. On the other hand, the chassis- dynamometer certified products tend to place more emphasis on the cold-start portion (about 40 percent of the total emission weighting). Emission threshold levels for malfunction detection would have to take this weighting into account.

In addition, many requirements of the current OI3D 11 rule are not measurable on the heavy duty engine dynamometer transient cycle. Starting aids, such as glow plugs and intake air heaters, are currently not activated during the heavy duty FTP test and therefore could not be tested for emissions impact per the current heavy duty certification guidelines. For compliance with the existing OBD I1 rule, the impact of a malfunction on emissions must be determined by analytical or other test methods.

Also, engines undergoing certification testing on an engine dynamometer cannot simulate a situation which a transmission fault results in an overspeed condition of the engine resulting in excess emissions. This issue currently plagues engine manufacturers of heavy duty engines that are used in medium duty vehicles. Again, either analytical or other methods would need to be used to determine the emissions impact, adding cost.

Another confounding issue touched on earlier in this paper was that the majority of industry participants in the heavy duty engine and vehicle market are not vert;icailly integrated. Engines are tested and certified in emission families, based on the highest emitter in the family. Because the engine manufacturer is not knowledgeable of every con- ceivable application of its product and because of all the possible combinations of driveshafts, axle ratios, transmissions, tire sizes and vehicle weights, it is nearly impossible to certify all possible combinations. Additionally, vehicle man-

ufacturers install several different engine models from several different engine manufacturers, making it more impractical to certify all possible combinations. Vertically integrated passenger car companies do not have this added burden; they control all aspects of the design and manufacture of all vehicle components they use. This must be factored in when investigating the need for a regulation.

Uptime demands of the customer require effective diagnostics. Failures affecting emissions typically have ;a

negative impact on the commercial customer, resulting in requests for easy diagnosis and immediate repair. An engine failure that can cause overfueling will likely lead to poor fuel economy.

According to the CARB OBD 11 regulation, manufacturers of loose heavy duty engines are allowed to use a durability demonstration engine rather than a durability demonstration vehicle. Some points of confusion arise when the vehicle system is integrated in a fashion where the electronic controls on the engine and those on the vehicle share tasks to meet the OBD I1 requirements. An example is where the task manager for OBD I1 diagnostics is in one control module and other control modules communicate to it the error conditions to be logged. The vehicle system meets the intent of OBD I1 but the emissions certificate holder, in most cases the engine supplier, is required to go to extra effort to simulate the vehicle environment in testing that the malfunction indicator lamp performed as it should--on when expected, off when expected. The advantage of the engine supplier being able to certify the engine alone is that there is not a need to duplicate and recertify every vehicle application. This makes good sense because the engine is the same in this example and therefore should not need to be recertified. Testing the engine in each vehicle application does not seem to be a value-added process. It would needlessly drive up the cost of compliance, a cost passed on to the end user.

The most recent changes made by heavy duty engine manufacturers of diesel engines to reduce emissions of oxides of nitrogen (NOx) and particulate matter (PM) have been accomplished by in-cylinder control methods. No electronically controlled heavy-heavy duty automotive diesel engine (as classified by C A B and EPA) certiked to meet 1995 emission requirements uses add-on devices such as oxidation catalysts and exhaust gas recirculation systems. Three-way catalysts, heated three-way catalysts, secondary air systems, evaporative purge systems and oxygen sensors are not used now and are not expected to be used in the near future.


CONCLUSIONS

It is expected that the heavy duty diesel engine industry will be able to meet the 1998 emission levels by using enhanced electronic control and comprehensive diagnostic systems to optimize in-cylinder combustion events. This is accomplished with higher fuel injection pressures, improved use of intake air control such as swirl and attention to fuel injection timing and rate shaping. It is not expected that any form of catalyst, exhaust gas recirculation or other add-on device will be used to meet the 1998 levels.

The next change in emission levels is not anticipated until 2004 and is currently under discussion with EPA and CARB. If add-on technologies for limiting emissions are incorporated on heavy duty diesel engines to meet these or other future emission standards, then an analysis to determine the need for mandating special diagnostics should be performed. As with any regulatory activity, technical feasibility and cost effectiveness of new diagnostic system requirements on heavy duty engines and vehicles must be demonstrated. When demonstrating this, one must recall that the demands of the heavy duty customer already include special attention to fuel economy, vehicle uptime and standardized diagnostics and serial communications.


References Industry Standards for Diagnostics and Serial Communications

Standards Code Heavy Duty Recornmen6

1. RP-1202

2. 51587

Titles or Descriptive Names I Approved Rev Date ?d Practices

ATA TMC Off-Board Diagnostic Standards 1/92

Joint SAEiTMC Electronic Data Interchange Between 1/88 1/94 Microcomputer Systems in Heavy-Duty Vehicle Applications

MS-DOSTM Interface for 51708 Communications 6/93 Ballot

Serial Data Communications Between Microcomputer Systems in 1/86 10193 Heavy-Duty Vehicle Applications -- Powertrain Control Interface for Electronic Controls Used in 12/89 Medium and Heavy Duty Diesel On-Highway Vehicle Applications -- OEMNendor's Interface Specification for Vehicle Electronic 1 2/92 Programming Station

ElectricaVElectronic Systems Diagnostic Terms, Definitions, 6/95 Abbreviations, and Acronyms for Heavy Duty Vehicles Draft

Recommended Practice for Serial Control and Communications 4/95 Network (Class C) or Truck arid Bus Applications Draft

Recommended Practice for Control and Communications Network 4/94 for Truck and Bus Applicatiorns Draft

Physical Layer, 250k bitslsec, Shielded Twisted Pair 12/94 - ---

I Data Link Laver 12. 5193913 1 I Network Laver 1 4/94

13. 51939171 Vehicle Application L.ayer 8/94

14. 51939173 Application Layer-Diagnostics 4/95 Ballot

Network Management Protocol 4/95 I Draft

16. 52214 Vehicle Electronic Programming Station (VEPS) System 11/92 Specification for Programming 51708-Capable Components at Draft OEM Assembly Plants --

17. JYYYY Vendor Component Pirogram Data File Interface for OEM 1 0194 Assembly Operations -- Draft

18. RP-TBD Under development by the ATA Th4C Study Group 5 subgroup Draft in development entitled Establishing a Standard for the Exchange of Electronic Service Information

Light Duty Recommended Practices 19. 51850 I Class B Data Communication Network Interface 9/88 5/94

20. 51930 I ElectricalElectronic Systems Diagnostic Terms, Definitions, Abbreviations and Ac~:onvms

1 6/88 6/93

Diagnostic Connector

OBD I1 Scan Tool

23. 51979 E/E Diagnostic Test Modes 6/94

24. 52008 Recommended Organization of Vehicle Service Information 25. 52012 Recommended Practice for Diagnostic Trouble Code Definitions 3/92 6/94

26. 5217811 Class B Data Communication Network Messages: Detailed Header 6/92 Formats and Physical .Address Assignments


Additional References

Standards Code

39. California Code of Regulations, Title 13, Section 1968.1-Malfunction and Diagnostic System Require- ments-1994 and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines (OBD 11).

Titles or Descriptive Names 1 Approved Rev Date

40. Environmental Protection Agency, Title 40 Code of Federal Regulations, Part 86, section 86.094- 17--Control of Air Pollution from New Motor Vehicles and New Motor Vehicle Engines; Regulations Requiring On-Board Diagnostic Systems on 1994 and Later Model Year Light-Duty Vehicles and Light-Duty Trucks (OBD).

41. CARB Manufacturers Advisory Correspondence (MAC) 92-07, July 17, 1992. (This is the CARB document that requires SAE 51930 on heavy duty vehicles for California markets.)

Light Duty Recommended

27. 3217812

28. J2 17813

29. 32 17814

30. 521 86

31. 52190

32. J2201

3 3. 32205

34. IS0 9141-2

35. ISOJDIS 14229 E

36. ISO/DIS 14230-1 E

37. ISOJDIS 14230-2 E

38. ISO/DIS 14230-3 E

42. CARB Manufacturers Advisory Correspondence Mail Out #94-16, March 31, 1994. Subject: Tamper Resis- tance for Adjustable Parameters on Emissions-Related Components. (This is the CARB document that requires SAE 52186 on heavy duty vehicles for California markets.)

44. Austin, J.W. and R.J. Weimer, "Service and Support of Electronic Products in the Trucking Industry," SAE Paper No. 871579, presented at the Future Transportation Technology Conference and Exposition, Seattle, WA, August 10-13, 1987.

Practices (continued)

Class B Data Communication Network Messages Part 2: Data Parameter Definitions

Class B Data Communication Network Messages-Part 3 Frame IDS for Single Byte Forms of Headers Class B Data Communication Network Messages Part 4: Target Address (Second Byte) for Three Byte Headers E/E Data Link Security

Enhanced E/E Diagnostic Test Modes

Universal Interface for OBD 11 Scan

Expanded Diagnostic Protocol for OBD I1 Scan Tools Road Vehicles-Diagnostic Systems-Part 2: CARB Requirements for Interchange of Digital Information

Road Vehicles-Diagnostic Systems-Diagnostic Services Specification

Road Vehicles-Diagnostic Systems-Keyword Protocol 2000 Part 1 : Physical Layer

Road Vehicles-Diagnostic Systems-Keyword Protocol 2000 Part 2: Data Link Layer

Road Vehicles-Diagnostic Systems-Keyword Protocol 2000 Part 3: Application Layer

45. Stamper, R.A., "A Second-Generation Approach to Service of Electronic Systems," SAE Paper No. 891681, presented at the Future Transportation Technology Con- ference and Exposition, Vancouver, BC, Canada, August 7-10, 1989.

6/93

9/93

9/93 Draft

919 1

6/93

6/93

6/94

2/94

2/95 Ballot

2/95 Ballot

2/95 Ballot

2/95 Ballot

46. Stepper, M.R., "Data Link Overview for Heavy Duty Vehicle Applications," SAE Paper No. 902215, presented at the Truck and Bus Meeting and Exposition, Detroit, MI, October 29-November 1, 1990.

47. Stepper, M.R., "51939 High Speed Serial Communi- cation, The Next Generation Network for Heavy Duty Vehicles," SAE Paper No. 931 809, presented at the SAE Future Transportation Technology Conference, San Antonio, TX, August 9-12, 1993.

43. European Union OBD: Diesel work being investigated by the On-Board Diagnostics Working Group of the EU subgroup entitled European Motor Vehicle Emissions Group (MVEG), chaired by Dr. Paul Greening, United Kingdom Department of Transport, London, England.


Documents

On-Board Diagnostics, A Heavy Duty Perspective · rods. Engines had rated horsepower occurring at 2100 rpm unless one was more fuel-efficiency conscious; then they could be ordered