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Scan Tool Basics This will help you prepare for the NC3 – Snap‐on Scan Tool Certification .  

Front‐Door vs Back‐Door Diagnostics      To diagnose a computer control system you can go to the “Front Door” or the “Back Door”.  The Front Door is where sensor data (input) enters and actuator data (output) leaves the computer.  You go in the Back Door by using a scan tool to find what the computer is thinking.  

Diagnosis often starts at the Back Door.  The back door is found at the data link connector (DLC) where you connect the scan tool to the vehicle.   On a modern vehicle you can use a scan tool to access the Back Door for multiple vehicle control modules such as the engine, transmission, instrument cluster, tire pressure monitor, ABS system, power windows, etc.   Back Door Checks include: Diagnostic Trouble Codes (DTC’s), Input and Output Data (called Parameter Identifiers or PID’s), Graphing PID Data (used to view the relationships between different PID’s), and using the diagnostic Troubleshooter.  The Troubleshooter software found in the scan tool will list procedures to test that component or system.   

The scan tool (back door) will help you decide which Front Door tests are needed to solve the problem.   Front Door tests can be made on input signals (from sensors to the computer), or output command signals used to control the various actuators (like fuel injection, ignition timing, etc.) just remember, The Front Door is what is actually happening outside of the computer and the Back Door is what the computer “thinks” is happening.  

 Scan tool data (input – output data) and Diagnostic Trouble Codes (DTC’s) are all found at the back door.  Once you know which system to check, you diagnose that system using Front Door diagnostic tests.   

 

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The scan tool is a BACK‐DOOR directional tool. It never tells you the cause of a problem, only what’s being affected and where to look.   The cause for the malfunction will almost always be found through the FRONT DOOR. 

Who needs to use a scan tool? 

     It the past only driveability or engine performance technicians needed to use a scan tool.  On modern vehicles you will often use a scan tool to bleed the brakes, perform and alignment, repair a power window, change the tires, or even change the oil.  

How do I connect the scan tool? 

     Here is a picture showing the controls of the Solus Pro which is the primary scan tool we will be using in this class.

 

Power ON the scan tool, then identify the vehicle you are working on  using the Thumb Pad and the Y or N buttons.  It is easy to use these scan tool control buttons once you have tried it a few times. 

   

 

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Here is what you see when you first turn on the Solus Pro 

 

As you progress through the menu, it will instruct you to use a specific key such as the K‐20 key or the S44 key.  Below is a picture of what those keys look like. 

  

These plug in to the long black communication cable for the Solus Pro.  

The next step is to find the Data Link Connector (DLC) inside your vehicle.   

 

The DLC is a 16‐pin connector found on OBDII equipped vehicles.  OBD‐II standards specify the DLC be located under the dash near the steering column.   If you can’t find it, the Solus Pro will tell you where the DLC is. 

 

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Once you have identified the vehicle on the scan tool, used the proper key, and connected the communication cable to the DLC, you will need to turn the ignition key to RUN.  The Solus Pro can now “talk” to the vehicle control modules. 

What can a scan tool do? Your scan tool can access many vehicle control modules.           The Powertrain Control Modules (PCM) will control your engine and transmission.  Modern vehicles have many more control modules.  There will be a control module for the instrument cluster, another module for the anti‐lock brakes, one for the air bags and often there is an electronic control module in each of the doors.   Some vehicles have over 30 different control modules. It is important to access these control modules to perform tasks such as setting tire pressure monitors, re‐initializing body controls like power windows, bleeding brakes, diagnosing dash gauges, etc. 

Your scan tool will display Diagnostic Trouble Codes (DTC’s).            Diagnostic Trouble Codes are set when the computer decides a system is not working correctly.  The computer will set a code and may illuminate the Malfunction Indicator Lamp (MIL) to alert the driver.    Diagnostic Trouble Codes only direct you to which system needs diagnosis, they will not tell you what to replace!  For help in diagnosing DTC’s Snap‐on scan tools provide the Fast‐Track Troubleshooter.  This is a large database of diagnostic procedures that can help you quickly find the root cause of the Diagnostic Trouble Code. 

Your scan tool will show all the Parameter Identifiers (PID’s)       PID’s are the name we use to represent all the input (sensor) and output (actuator) data.  Input Data comes from vehicle sensors and Output Data is commands sent to the vehicle actuators.  PID data is the “Back Door” of your computer system and shows what the control module thinks is happening.  For instance the PCM monitors the Engine Coolant Temperature.  The PID for engine temperature is ECT.  When it is cold the PCM decides to add more fuel by keeping the fuel injectors on longer.  The input signal is from the ECT which is a sensor.  To add more fuel an output signal goes to the fuel injectors, which are actuators.   

 

 

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PID data will be numbers (like 755 RPM or TPS (throttle position) of 93%.  Some scan tools will display only those numbers (Text).  With the Solus Pro you can view PID data three different ways.  You can view the data as Text, a PID List, or a Graph.  By graphing PID data you can view the relationship between any sensor and actuator.  It will show how the PID data changes over time. 

 

 

Here we are viewing the relationship between the TPS (Throttle Position Sensor) and engine RPM.  The RPM should go higher when we open the throttle and lower as we close the throttle.  At the left end of the graph we see the throttle is held steady about half way open and the RPM is going Up.   When the throttle is allowed to close the RPM goes down.  This is all normal operation.  Then the TPS drops to zero, but the RPM goes back up.  Opening the throttle is what causes engine RPM to increase, however the PID data shows the TPS as fully closed.  This relationship of closed throttle while RPM goes UP indicates there is a defect in the TPS sensor or the wires going to the TPS. 

   

 

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Your scan tool can run Functional Tests that fall into four categories.   1) Information tests, 2) Toggle tests, 3) Variable Control tests, and 4) Reset tests.           Information tests provide information such as the VIN number and the Calibration Part Number.  This information is useful when checking to see if the computer has been updated, or when installing a replacement control module.         Toggle tests allow you to ask the control module to turn ON or OFF various actuators.  An example would be to request that the Malfunction Indicator Lamp be turned ON or OFF.  This is an easy way to test the MIL bulb to see if it is blown out.  Another test might be to toggle ON/OFF the fuel injectors one at a time to see if the engine RPM drops the same amount for each cylinder. Toggle tests are found under Functional Tests >> Output Controls.          Variable Control tests are also found in Functional Tests >> Output Controls.  A variable test can command an actuator to run through it’s full range of adjustment.  For example the customer is complaining that the fuel gauge will not go past ½ full.  By selecting Functional Tests >> Output Controls >> Variable Control >> Fuel Gauge Enable (%) you can command the fuel gauge to display from 0% (empty) to 50% (1/2 full) to 100% (full).  If the gauge now reads full, the problem is most likely in the fuel sending unit.   If the variable control test cannot get the gauge to read past ½ full, the dash gauge must be defective.           Reset tests are necessary when installing certain components.  For example on some engines replacing the crank position sensor (CKP) will require the computer to “re‐learn” the new CKP sensor signal.  This reset test is called CKP Variation Learn.  On these engines, if you replace the sensor without performing the reset test, the engine may not idle at the correct speed. 

When should I use the scan tool? 

When you are diagnosing any engine performance issue the scan tool should be one of the first diagnostic steps.  By looking for codes or viewing PID data you find which direction your diagnostic path should take.  When diagnosing it is a good idea to check for Technical Service Bulletins (TSB’s).  SnapOn scan tools will provide troubleshooter software that uses this TSB information to help with your diagnosis.  While a scan tool will seldom, if ever, isolate the cause of a problem, it will send you in the right direction and guide you as to what to check next. 

 

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The MIL lamp is ON but there are no codes! 

Upon occasion you will have a vehicle with the Malfunction Indicator Lamp illuminated but your scan tool does not display any code.  All this means is that you have not looked in the proper control room.  Powertrain Control Modules on modern vehicles all have two basic “Control Rooms”.  They are the Original Equipment Manufacturer (OEM) room and the On Board Diagnostic (OBD‐II) room.   

 

OEM software uses communication standards set by the specific vehicle manufacturer.  There are many different standards used and they change depending upon model and year.  This is why you need the proper Key hooked into the Modis Pro communication cable! 

OBD‐II software uses a communication standard set by the Environmental Protection Agency.  All manufacturers must use the same communication standard for OBD‐II functions.   

The OBD‐II room is in charge of the MIL.  It is the OBD‐II control room that will decide when to turn on or off the Malfunction Indicator Lamp.  It also captures and stores PID data present at the time the MIL was turned ON.  This is called Freeze Frame data and can be very useful in deciding what was happening when the failure occurred. 

An experienced technician will check both the OEM room and the OBD‐II room when diagnosing the vehicle. 

 

 

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The only way to learn a scan tool is to practice with it! 

The more you use it, the more powerful of a diagnostic tool it will become.  As a beginner you will not know what many of the PID data abbreviations stand for.  Even experienced technicians will not know them all.  When you find a PID you do not understand, go to: Troubleshooter >> Fast Track Data Scan (Normal Values).  Here the Solus Pro will tell you what that PID means and provide normal or typical data values for that PID.   Do not hesitate to explore the many features of the Troubleshooter. 

Which scan tool should I purchase?  

The very cheapest scan tools are often called code readers.  They will only give OBD‐II generic codes.  There are many Diagnostic Trouble Codes (DTC’s) stored in the OEM room of the PCM that will not show up on a code reader.  Also code readers will not display PID data which is vital to diagnosing a modern vehicle. 

Because all OBD‐II control rooms use a standardized communication protocol some less expensive scan tools will only talk to the OBDII control room.  They will show DTC’s and PID data available in the OBD control room only.  Remember how the OBDII room turns on the MIL?  Just because the MIL lamp is OFF does not mean there are no codes.  The OEM room will store codes and PID data not found in the OBD room.   A professional needs a scan tool that talks to both the OBDII room and the OEM room found in modern vehicles.   

A quality scan tool with all the features you need to diagnose modern vehicles is not cheap, and they get more sophisticated every year.  For this reason I always caution students to wait on buying a scan tool.   You won’t make much money when you first start, and the shop you work for should have one or more scan tools to help you with the tasks an entry level‐apprentice technician performs.   

It takes time and effort to gain experience and competence.  If you work hard and keep studying you soon will be earning more money to help buy this expensive tool.  Also, by the time you really need to purchase your own scan tool they will be faster, better, and maybe even cheaper. 

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Scan Tool Help Copyright AA1Car.com

A scan tool is a must for automotive diagnostic work today. When your Check Engine Light is on, you have to access the vehicle's onboard diagnostics with a code reader, scan tool or scanner software to find out what's wrong. A scan tool allows you to read faul codes and other diagnostic information.

READING TROUBLE CODES

On most 1995 and older pre-OBD2 domestic vehicles, diagnostic trouble codes can be read manually by grounding or jumping certain terminals on the vehicle's diagnostic connector. This puts the powertrain control module (PCM) into a self-diagnostic display mode, causing it flash out the code via the Check Engine Light (Malfunction Indicator Lamp or MIL). You then look up the code number in a reference chart (such as DTC Code Finder) to find out why the light is on.

The problem with reading manual flash codes is that (1) they are no longer used on most 1996 and newer vehicles (one exception is Nissan), and (2) counting the series of flashes can be confusing. Most flash codes use a combination of long and short flashes to indicate double digit codes, and if the vehicle has more than one code, it may be tricky to tell when one code ends and the next one begins. So the preferred method of reading codes on older vehicles is to use a code reader or scan tool.

On 1996 and newer vehicles with OBD2, there are no manual flash codes. You must have a code reader or scan tool to read the codes.

CODE READERS

The most basic diagnostic tool is a code reader. A code reader can access and display codes from your vehicle's computer. The least expensive models only display a number

while the better ones also provide a definition (some are even bilingual and can display in English, Spanish or French). Code readers typically sell for under $50. A code reader can also clear codes to turn off the Check Engine light. Some code readers can also display the "ready" status of various OBD II monitors (ready means the monitor has completed its self-check process). But a code reader is NOT a scan tool because it only reads and clears codes. It does NOT display any sensor data or other system operating information. To read sensor and other system data, you need some type of scan tool or scanner software.

An important point to keep in mind here is that a fault code by itself does NOT tell you which part needs to be replaced. The code only tells you that a fault has been detected, not what caused it. The code serves as a starting point for further diagnosis. Many people don't understand this and assume an inexpensive code reader is all they

need to "diagnose" and repair their vehicle.

Also, don't assume all code readers display all codes. They all display "generic" or "global" OBD2 codes ("P0" codes). But some do not display manufacturer "enhanced codes" ("P1" codes), or if they do, the list of codes may be limited to domestic vehicles (Ford, GM & Chrysler) and not include any enhanced codes for Asian or European vehicles.

Something else to check before you buy is the model years the code reader can access. Most code readers are for 1996 and newer OBD2 vehicles with a standard OBD2 16-pin connector. Most code readers cannot read codes on 1995 and older cars or trucks because the connectors are different. However, vehicle-specific code readers are available for older GM, Ford or Chrysler applications. The same is true for BMW, MINI and some other import applications.

Something else to keep in mind about code readers (and scan tools), is that the list of new DTCs and system data grows with every new model year. Last year's tool may not work on next year's models. Tools get out-of-date VERY quickly, and have to be updated with new software via plug-in memory chips, cartridges or internet downloads from the tool supplier. If you are shopping on ebay for a used code reader or scan tool, make sure it will work on your vehicle, or can be updated to your vehicle.

SCAN TOOLS

For advanced diagnostics on today's vehicles, a full feature scan tool is an absolute must. Scan tools for do-it-yourselfers can display sensor values and system data, but DIY scan tools cannot perform various system self-tests such as checking the operation of the fuel pump, cooling fan(s), idle speed control motor or solenoid, EGR solenoid, A/C compressor clutch, fuel injectors, EVAP leak test, EVAP purge controls, etc. This level of diagnostics requires a professional level scan tool (which are EXPENSIVE!) with bidirectional (two-way) communication capability and the proper software for accessing and running these type of tests. Scan tools have different ranges and capabilities. Entry level "generic" scan tools typically sell for less than $200. They can read and clear codes, display the status of the various OBD II system monitors, and display basic operating data such as loop status (Open or Closed), airflow, coolant temperature, oxygen sensor outputs, throttle position and other sensor readings, and fuel trim values for diagnostic purposes. Most of these tools are fairly versatile and work on all domestic makes (Ford, GM & Chrysler), but may require additional software for Asian and/or European applications.

Entry level scan tools that are sold in auto parts stores are usually designed for do-it-yourselfers, and lack bidirectional communications capability for liability reasons. They

may also display only a limited number of "PIDs" (Performance Information Data such as sensor values, switch status and other operational data) compared to a professional level scan tool or factory scan tool.

DIY Scan Tool Product Information

Click on the following links to view product information from scan tool manufacturers about each of their products:

Actron Uscan for Smart Phones (New product June 2013) Actron CP9145 Scan Tool Actron CP9185 Scan Tool Actron CP9575 Scan Tool Actron CP9580 Scanner Plus Actron AutoScanner Plus with Code Connect (YouTube video demo) Equus_Innova 3040S Scan Tool Equus_Innova 3040 Scan Tool (YouTube demo video) Equus_Innova 3050BSRS Scan Tool with Air Bag capability Equus_Innova 3120-3130 Scan Tools Equus_Innova 3160 Scan Tool (YouTube video demo)

PROFESSIONAL LEVEL SCAN TOOL FEATURES

The more advanced aftermarket professional grade scan tools, by comparison, can do most of the same things an OEM factory scan tool can do. They can access and display all or most of the PIDs (with the proper software), and they can access and run all or most of the OEM self-tests (again, with the proper software).

The better tools typically have better displays, too. These include larger LCD screens with color graphics. The tool may also have multi-channel scope function that allows data to be displayed as a graph or waveform. This makes is easier to detect certain kinds of problems that may occur too quickly to notice when looking at numerical data. Many scan tools also have a "flight recorder" capability that allows data to be captured while the vehicle is being driven, for later analysis. An add-on 5-gas exhaust gas emission analyzer may also be an option.

Another feature that's available in many professional level scan tools is the ability to flash reprogram PCMs. Flashing a PCM with updated software may be necessary to correct a driveability or emissions issue. Flashing may also be necessary if the PCM is replaced. The other option is to get a J2534-compliant "pass-thru" tool that serves as an interface between the vehicle's PCM and a laptop or desktop PC.

NOTE: Some claims can be misleading. A vendor may say their product or software package covers a long list of makes and models, but it may be only generic OBD II information. They may not even have enhanced codes for the applications listed. Others may provide all the OBD II codes but no additional codes for ABS, air bags or other systems beyond the engine and powertrain. Some may have limited diagnostics and not include all the factory tests or procedures. If you are not sure exactly what is or is not included, ask before you buy.

Another cost associated with buying a professional scan tool is the cost of annual software updates. Updates are essential for keeping up with changes that occur every year. Update subscriptions can cost up to $800 per year.

If you are looking for info on a particular scan tool, go to the tool supplier's website and browse their product information and/or training videos:

CLick Here to Vew Auto Enginuity scan tool training videos Click Here to View OTC scan tool training videos Click Here to View Snap-On Scan tool training videos

OEM OR AFTERMARKET SCAN TOOL?

OEM factory scan tools provide full access to virtually everything, but are very expensive compared to many aftermarket general purpose scan tools (though some of the high end aftermarket tools also cost thousands of dollars depending on their features). An OEM scan tool may cost $5000 up to $12,000 or more!

OEM scan tools include the Tech II for General Motors applications, New Generation Star (NGS) tester for Ford/Lincoln/Mercury, DRB III for Chrysler, and a list of others for the Asian and European makes. Some of these are now obsolete, having been replaced by more advanced PC-based scanner software in dealerships. Even so, for home diagnostic work, you can often find one of these older scan tools reasonably prices on ebay.

Factory scan tools generally provide access to all the diagnostic trouble codes (both "generic OBD II" and "enhanced"), all the on-board self-test procedures, and all of the other on-board electronics beyond engine performance and emissions such as the body control module, ABS module, air bag module, suspension module, climate control module and so on. The OEM scan tool can also be used to "reset" or "initiate" a module if it has been replaced (which is often necessary before the module will function correctly)> Often this involves a special "relearn" procedure that

may only be available with the factory scan tool.

The only drawback with OEM scan tools is that most (with some exceptions) are designed to only work on ONE make of vehicle, not all makes and models. Consequently, they are well suited for new car dealer technicians but not general repair shop technicians who usually work on all makes and models.

Most technicians can't afford to own a separate scan tool for each and every vehicle they work on, so most opt for a general purpose scan tool and add software and hardware to expand its capabilities as needed. Some may also buy one or two OEM scan tools if they do a lot of work on a particular make (GM, for example, or an import). And they may also have a basic code reader for making quick code checks.

IS THE SCAN TOOL CAN COMPLIANT?

In recent years, the electrical systems on vehicles on late model vehicles have been using a new onboard communications protocol called CAN or Controller Area Network. CAN started phasing in in the early 2000s, and became standard on all 2008 and newer cars and light trucks. CAN uses a much higher baud rate to allow faster communication between modules. Because of this, CAN vehicles require a scan tool that is CAN-compliant for diagnostics. Most older scan tools cannot be upgraded to read the newer CAN vehicles. So if you are buying a used older scan tool, keep that in mind.

. Innova 3140 CAN-compliant scan tool. . .

SCANNER SOFTWARE

In addition to dedicated scan tools, you can also buy software that transforms a laptop or desktop PC, PDA, tablet or smart phone into a code reader or scan tool. Some of these offer very basic functions only while others run essentially the same software as an OEM scan tool.

The simplest and cheapest packages that sell for a couple hundred dollars or less essentially give you the ability to plug a laptop, PDA, tablet or smart phone into the diagnostic connector on a 1996 or newer vehicle and use it as a code reader to display and clear generic OBD2 fault codes. The better packages include enhanced codes for specific vehicle applications, and also may include the ability to display various PIDs such as sensor voltages, switch status and so on. The best software also includes graphics for displaying sensor voltages and other data.

Scanner software for a laptop, PC, tablet or smart phone requires either an interface cable that plugs into the OBD2 connector, or a WiFi or Bluethooth connection so your vehicle can communicate with your electronic device. The scan tool software, by itself, is useless without the cable or wireless interface that connects your computer or electronic device to your vehicle. If you are resourceful and want to save a few bucks, there are numerous sources on the Internet where you can buy interface cables separately, or kits or plans to build your own USB OBD cable.

One of the advantages of using a laptop or desktop PC as a scan tool is having a large display (which makes it easier to read and can display more information on a single page). Most laptops have a screen that measures 12 to 17 inches diagonally, while most PC monitors range in size from 16 to 22 inches or larger. If you have an old PC sitting around gathering dust, you can convert it into a large display color scan tool at a minimal cost (typically $250 to $500 or less for the software, including the interface cable).

Another advantage of using a computer as a scanner is that it can easily be updated by downloading the latest software via the internet. This also can be done with most newer scan tools as well (using a PC as an interface with a USB cable). The updates for DIY scan tools are often free, but for professional scan tools there is usually a fee or yearly subscription to pay.

Dedicated scan tools, by comparison, are designed to be scan tools and nothing else. You cannot surf the Internet with them or check your e-mail or Facebook page. They are for diagnosing cars only. Many professional-grade scan tools have additional hardware circuitry and test leads that allow you to use the same tool as a multimeter or digital oscilloscope to measure voltages, resistance and current. This is an extremely useful feature to have and reduces the need for additional test equipment.

SCAN TOOLS WITH SCOPE DIAGNOSTICS

Many high end professional scan tools also have the added ability to function as graphing multimeters or digital storage oscilloscopes. Being able to display sensor voltages as waveforms makes it much easier to detect problems that are nearly impossible to diagnose any other way.

If you are looking for a multi-purpose tool that can be used as a scanner, multimeter and scope, choose one that can display more than one waveform at a time. Many professional scan tools can simultaneously graph and display up to four different PIDs.

When a scope is hooked up to a sensor or circuit, it shows what is actually going on inside that device or circuit. Voltage is displayed as

a time-based waveform. Once you know how to read waveforms, you can tell good ones from bad ones. You also can compare waveforms against scan tool data to see if the numbers agree (which is a great way to identify internal PCM faults).

A scope also allows you to perform and verify "action-reaction" tests. You can use one channel to monitor the action or input, and a second, third or fourth channel to watch the results. For example, you might want to watch the throttle position sensor, fuel injector waveform, crank sensor signal and ignition pattern when blipping the throttle to catch an intermittent misfire condition.

Using a scope does require a working knowledge of scope basics as well as the limitations of the scope you are using. Like scan tools, different scopes have different capabilities, so study and compare before you buy.

SCAN TOOL COMPARISON REPORT

For an up-to-date report compiled by the National Automotive Service Task Force (NASTF) on which scan tools are required for which vehicle applications, Click Here .

If you would like to read one shop's experience with scan tools and why they own what they own, Click Here

To find out more about Aftermarket scan tool limitations, and the problems scan tool companies have getting current service information from the vehicle manufacturers, Read This NASTF Report (January 2011).

WHICH SCANTOOL DO TECHNICIANS PREFER?

According to a recent (2011) user survey of 400 technicians by iATN (International Automotive Technicians Network), the most popular scan tool form factors are as follows: 61% prefer a hand-held scan tool 28% prefer a laptop with scanner software 11% prefer a tablet with scanner software

Those who prefer a traditional hand held scan tool say the units are much faster and easier to use than a laptop or tablet. However, many of the newest professional level scan tools are using Windows-based scanner software in a custom hand held form (Snap-On Modis, Verus, Verdict, etc.). We will probably see more development of Windows scanner software for tablets and custom apps for iPhones and other smart phones as time goes on.

ADVANCED SCAN TOOL DIAGNOSTICS

For advanced scope diagnostics, you will want to learn how to access Mode 06 information on a scan tool (most tools that cost upwards of $200 can access Mode 06 today, but you have to know how to find it because it is not clearly marked. Mode 06 data is the raw hexadecimal code data the engine computer looks at when it runs system monitors. This is useful information to access when a vehicle is experiencing a no-code driveability problem, to verify whether or not a particular sensor or circuit is operating within its specified MIN and MAX values, and to verify a sensor or other component is working properly after it has been replaced.

Information on translating and converting Mode 06 hex code for Ford and GM can be found on the International Automotive Technicians Network website (www.iatn.com). Go to the "Technical Resources" menu, then look in the Ford and Toyota sections. The Mode 06 information is in a downloadable PowerPoint presentation by Paul Baltusis of Ford Motor Company, called "An Introduction to Vehicle Networks, Scan Tools and Multiplexing."

OTHER THINGS YOU WILL NEED IN ADDITION TO A SCAN TOOL

When you buy a scan tool, don't expect to become a diagnostic expert overnight. All scan tools have a learning curve, and it takes some time to figure out what the tool will do (and what it cannot do), which PIDS and other sensor data you should be looking at when troubleshooting different kinds of faults, and what the information means. Scan Tool Companion is a handy reference program that can help you make the most of your scan tool. The program runs from a CD on a laptop or Desktop Windows PC, and tells you which PIDs and data you need to look at by symptom, by code or by system. It also includes background reference information on engine sensors, OBD2 monitors, OBD2 emissions testing, and the operation of the engine management

system. This is a "must have" reference program for any scan tool user.

Something else to keep in mind is that a scan tool by itself can't fix anything. It takes a brain to operate and use the information provided by the tool. You need to be knowledgeable about OBD2, engine management systems and sensor diagnosis. You also need access to current service information, technical service bulletins and electrical wiring diagrams. If you do not know how a sensor or circuit functions, what causes a code to set, or how a particular sensor or circuit is wired, how are you going to fix the fault?

You also can't rely on codes alone to identify all problems. Many problems never set a code. Some codes can be misleading because of the combination of circumstances that caused them to be set. Other codes may be false codes that never can be eliminated by normal repair procedures. You may have to reflash the computer to fix the problem.

The best advice here is to always check for TSBs, whether you find any codes or not. In many instances, there will be a TSB that covers the problem and will save you hours of frustration.

Click Here to Look up Technical Service Bulletins for Your Vehicle

In conclusion, the more time and research you put into choosing a scan tool, the better satisfied you will be. Check with your equipment suppliers or the sources listed below for specific product models, features and prices. Spend some time on the Internet researching the various alternatives. Do your homework and you will find the tool (or tools) that are right for you.