Audi CAN Data Bus

7/26/2019 Audi CAN Data Bus

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Learning + Transformation3800 Hamlin RoadAuburn Hills, MI 48326Printed in U.S.A.October 1999

Self-Study ProCourse Numbe


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Audi of America, Inc.Service TrainingPrinted in U.S.A.Printed 10/99Course Number 971903

All rights reserved. All information containedin this manual is based on the latest productinformation available at the time of printing.The right is reserved to make changes at anytime without notice. No part of this publicationmay be reproduced, stored in a retrievalsystem, or transmitted in any form or by anymeans, electronic, mechanical, photocopying,recording or otherwise, without the priorpermission of the publisher. This includes text,figures and tables.

Always check Technical Bulletins and theAudi Worldwide Repair Information Systemfor information that may supersede anyinformation included in this booklet.


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Contents

Introduction ............................................................................. 1

CAN Data Bus .......................................................................... 2

Data Transfer, The CAN Data Bus,The Principle of Data Transfer,What Components Make Up a CAN Data Bus?,Data Transfer Process

Data Transfer ........................................................................... 8What Does the CAN Data Bus Transfer?

Function ................................................................................. 10How is a Data Protocol Produced?, CAN Data Bus Allocation,Sources of Interference

CAN Data Bus in the Drive Train .......................................... 15The Data Bus in the Drive Train, The Information in theDrive Train, Networking of the Control Modules in theDrive Train, Self-Diagnosis of the CAN Data Bus in theDrive Train

CAN Data Bus in the Convenience System ........................ 21Future Use of the CAN Data Bus in the ConvenienceSystem, The Features of the CAN Data Bus in theConvenience System, Information in the Convenience

System, Networking of Control Units in the ConvenienceSystem, The Self-Diagnosis of the CAN Data Bus in theConvenience System

Teletest ................................................................................... 29Audi CAN Data Bus Teletest and Answer Form

The Self-Study Program is not a Workshop Manual!

Precise instructions for testing, adjustment and repair can befound in the appropriate Workshop Manual.

Important/Note!

New!


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Introduction

The requirements relating to driving safety,driving comfort, exhaust emissions and fueleconomy are becoming ever more

stringent.

This entails more intensive informationexchange between control units. A well-engineered solution is necessary to ensurethat the electrics/electronics in the vehiclestill remain manageable and do not take uptoo much space.

SSP 186/01

The CAN data bus by Bosch is such asolution. It was developed specially forautomobiles and is used by both

Volkswagen and Audi. CAN stands forController Area Network and means thatcontrol modules are networked andinterchange data.

In this Self-Study Program we will explainto you the design and functionof the CAN data bus.

A CAN data bus can be compared to apassenger bus.

While the passenger bus transports a largenumber of persons, the CAN data bustransports a large volume of information.


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Engine Speed

Fuel Consumption

Throttle Valve Position

Engine Intervention

Upshift/Downshift

CAN Data Bus

Data Transfer

What are the possible options for data

transfer in vehicles at present?

Option No. 1:

Each item of information is exchangedover a separate wire.

Option No. 2:

All information is exchanged betweencontrol modules along a maximum oftwo wires: the CAN data bus.

Conclusion:

A separate wire is required for each itemof information.

As the volume of additional informationincreases, so does the number of wiresand the number of pins on the controlmodules.

Motronic Engine ControlModule (ECM) J220

Transmission ControlModule (TCM) J217

Therefore, this data transfer mode is onlysuitable for exchanging a limited volume ofinformation.

SSP 186/04

The figure below shows you option

No. 1, where each item of informationis transferred along a separate wire.

A total of five wires are required for datatransfer in this case.


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CAN Data Bus

In contrast to option No. 1, in option No. 2

illustrated below, all information istranferred along two wires in the CANdata bus.

The same data is transferred along the twobidirectional wires of the CAN data bus.

You will find further information in this Self-Study Program.

Conclusion:

With this data transfer mode, allinformation is transferred along two wiresregardless of the number of participatingcontrol modules and the volume ofinformation involved.

Engine Speed

Fuel Consumption

Throttle Valve Position

Engine Intervention

Upshift/Downshift

Motronic Engine ControlModule (ECM) J220

Transmission ControlModule (TCM) J217

Data transfer with the CAN data bus wouldtherefore make sense if a large volume ofinformation is exchanged between controlunits.

SSP 186/05


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The CAN Data Bus

is a type of data transfer between control

modules. It links the individual controlmodules to form an integrated system.

The more information a control module hasregarding the state of the overall system,the better it can coordinate the individualfunctions.

The following components in the drivetrain form an integrated system:

the Engine Control Module (ECM) the Transmission Control Module(TCM)

the ABS Control Module (w/EDL) Haldex Control Module

The following components can be usedin the convenience system to form anintegrated system:

the central control module and

the door control modules

Benefits of the Data Bus:

If the data protocol is extended toinclude additional information, onlysoftware modifications are necessary.

Low error rate through continuousverification of the transmittedinformation by the control modules aswell as additional safeguards in thedata protocols.

Fewer sensors and signal lines throughthe multiple use of a sensor signal.

High-speed data transfer is possiblebetween control units.

More space available through smaller

control modules and smaller controlmodule plugs.

The CAN data bus conforms tointernational standards and thereforefacilitates data interchange betweendifferent makes of control unit.

CAN Data Bus

SSP 186/02

ABS Control Module(w/EDL)

Door Control Module(Future Models)

Central ControlModule

Engine ControlModule (ECM) Transmission Control

Module (TCM)

Haldex ControlModule


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CAN Data Bus

The Principle of Data Transfer

Data transfer with the CAN data bus

functions in much the same way as atelephone conference.

A subscriber (control module) speaksdata into the line network while the othersubscribers listen in to this data.

Some subscribers will be interested in thisdata and will utilize it. The other subscriberswill choose to ignore this data.

SSP 186/06

Control Module 3

Control Module 1 Control Module 2

Control Module 4

Data Bus Line


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CAN Data Bus

What Components Make Up aCAN Data Bus?

The CAN data bus comprises a controller, atransceiver, two data bus terminals and twodata bus lines.Apart from the data bus lines, thecomponents are located in the controlmodules. The functions of the controlmodules are the same as before.

They have the following tasks:

The CAN Controller

receives the transfer data from themicrocomputer integrated in the controlmodule. The CAN controller processes thisdata and relays it to the CAN transceiver.Likewise, the CAN controller receives datafrom the CAN transceiver, processes it andrelays it to the microcomputer integrated inthe control module.

The CAN Transceiveris a transmitter and receiver in one. Itconverts the data which the CAN controller

supplies into electrical signals and sendsthis data over the data bus lines.Likewise, it receives data and converts thisdata for the CAN controller.

The Data Bus Terminalis a resistor. It prevents data sent frombeing reflected at the ends and returning asan echo. This would corrupt the data.

The Data Bus Linesare bidirectional and transfer the data. Theyare referred to as CAN High and CAN Low.

SSP 186/03

Transmission Control Module(TCM) J217 with CAN Controllerand CAN Transceiver

Motronic Engine Control Module (ECM)J220 with CAN Controller and CANTransceiver

Data Bus Terminal

Data Bus Line

Data Bus Terminal


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CAN Data Bus

The data bus does not have a designatedreceiver. Data is sent over the data bus andis generally received and evaluated by all

subscribers.

Data Transfer Process:

Supplying the Data

The control module provides data to theCAN controller for transfer.

Sending Data

The CAN transceiver receives data fromthe CAN controller, converts it intoelectrical signals and sends them.

Receiving Data

All other control modules networked with

the CAN data bus become receivers.Checking Data

The control modules check whether theyrequire the data they have received for theirfunctions or not.

Accepting Data

If the received data is important, it is

accepted and processed. If not, it isignored.

SSP 186/07

AcceptData

CheckData

ReceiveData

ProvideData

SendData

ProvideData

SendData

AcceptData

CheckData

ReceiveData

Data Bus Line

Control Module 1 Control Module 2 Control Module 3 Control Module 4


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Data Transfer

The Seven Areas:

The start field

marks the start of the data protocol. A bitwith approximately 2.5 or 5.0 Volts(depending on system) is sent over theCAN High Line and a bit with approximately0 Volts is sent over the CAN Low Line.

The status fielddefines the level of priority of the dataprotocol. If, for instance, two controlmodules want to send their data protocolsimultaneously, the control module with

the higher priority takes precedence.

The check fielddisplays the number of items ofinformation contained in the data field.This field allows any receiver to checkwhether it has received all the informationtransferred to it.

In the data field ,information is transferred to the other

control modules.

The safety fielddetects transfer faults.

In the confirmation field ,the receivers signal to the transmitterthat they have correctly received the dataprotocol. If an error is detected, thereceivers notify the transmitter of thisimmediately. The transmitter then sends

the data protocol again.

The end fieldmarks the end of the data protocol. This isthe last possibility to indicate errors whichlead to a repeat transfer.

SSP 186/09

SSP 186/10

SSP 186/11

SSP 186/12

SSP 186/13

SSP 186/14

SSP 186/15


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In principle, the CAN data bus functions in

exactly the same way.

The transceivercan also generate two different bit states.

Status of bit with the value 1 Transceiver open, switches to 2.5 Volts

in the drive train system (conveniencesystem: approximately 5.0 Volts)

Voltage applied to data bus line:approximately 2.5 Volts in the drivetrain system (convenience system:approximately 5.0 Volts)

Function

How is a Data Protocol Produced?

The data protocol comprises a string of

several bits. Each bit can only have statusor value 0 or 1.

Here is a simple example to explainhow a status with the value 0 or 1is generated:

The light switchswitches a light on or off. This meansthat the light switch can have twodifferent states.

Status of the light switch with thevalue 1 Switch closed Lamp on

Status of the light switch with thevalue 0 Switch open Lamp is not on

Status of the bit with the value 0 Transceiver closed, switches to ground Voltage applied to data bus line:

approximately 0 Volts

SSP 186/17

SSP 186/18

CANTransceiver

CANTransceiver

SSP 186/16

5 Volts

0 Volts

5 Volts

0 Volts


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Function

The table below shows you howinformation can be transferred with twoconsecutive bits.

With two bits, there are four possiblevariations.One item of information can be assigned toeach variation and is binding for all controlmodules.

Example:

If bits 1 and 2 are transmitted with

0 Volts, this indicates that the electricwindows are in motion and that the coolanttemperature is 10 C.

The table below shows you how thenumber of items of information increaseswith each additional bit.

The higher the number of bits, the moreitems of information can be transferred.

The number of possible items of informationdoubles with each additional bit.

Bit Variants Possible Bit Variants Possible Bit Variants PossibleContaining Information Containing Information Containing Information

1 Bit 2 Bits 3 Bits

0 Volts 10 C 0 Volts, 0 Volts 10 C 0 Volts, 0 Volts, 0 Volts 10 C

5 Volts 20 C 0 Volts, 5 Volts 20 C 0 Volts, 0 Volts, 5 Volts 20 C

5 Volts, 0 Volts 30 C 0 Volts, 5 Volts, 0 Volts 30 C

5 Volts, 5 Volts 40 C 0 Volts, 5 Volts, 5 Volts 40 C

5 Volts, 0 Volts, 0 Volts 50 C




Possible 2nd Bit 1st Bit Graphic Electric Window Status Information onVariation Information Coolant Temperature

One 0 Volts 0 Volts in motion 10 C

Two 0 Volts 5 Volts not moving 20 C

Three 5 Volts 0 Volts within range 30 C

Four 5 Volts 5 Volts upper stop recognition 40 C


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Function

SSP 186/19

Data Bus Line

CAN Data Bus Allocation

If more than one control module wants to

send its data protocol simultaneously, thesystem must decide which control modulecomes first.The data protocol with the highest priorityis sent first. For safety reasons, the dataprotocol supplied by the ABS ControlModule (w/EDL) is more important than thedata protocol supplied by the TransmissionControl Module (TCM).

How are allocations made?

Each bit has a value, and this value isassigned a weighting. There are twopossibilities: high weighting or lowweighting.

How is the priority of a data protocolrecognized?

A code comprising eleven bits is assignedto each data protocol depending on itspriority in the status field.

The priorities of three different dataprotocols are shown in the table below.

Priority Data Protocol Status Field

1 Brake I 001 1010 0000

2 Engine I 010 1000 0000

3 Transmission I 100 0100 0000Bit With Value Weighting

0 Volts 0 HighWeighting

5 Volts 1 Low Weighting


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Function

All three control modules start sending theirdata protocol simultaneously. At the sametime, they compare the data bit on the data

bus line.If a control module sends a low weightingbit and detects a high weighting bit, thecontrol module stops sending and becomesa receiver.

Example:

Bit 1: ABS Control Module (w/EDL)

transmits a high weighting bit.

Motronic Engine Control Module (ECM)also transmits a high weighting bit.

Transmission Control Module (TCM)transmits a low weighting bit anddetects a high weighting bit on the databus line. Thus, it loses its priority statusand becomes a receiver.

Bit 2: ABS Control Module (w/EDL)

sends a high weighting bit.

Motronic Engine Control Module (ECM)transmits a low order bit and detects ahigher weighting bit on the data busline. This, it loses its priority status andbecomes a receiver.

Bit: 3: ABS Control Module (w/EDL)

has the highest priority and thusreceives the allocation. It continues to

send its data protocol until it ends.

After the ABS Control Module (w/EDL) hasfinished sending its data protocol, the othercontrol modules try again to transmit theirdata protocol.

SSP 186/20

ABS Control Module (w/EDL)

Motronic Engine ControlModule (ECM)

Transmission ControlModule (TCM)

Data Bus Line

Low Weighting

High Weighting

Transmission Control Module(TCM) Loses Priority Status

Motronic Engine Control Module(ECM) Loses Priority Status


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Function

Sources of Interference

Sources of interference in the vehicle are

components which produce sparks or inwhich electric circuits are open or closedduring operation.

Other sources of interference includemobile telephones and transmitter stations,i.e. any object which produceselectromagnetic waves. Electromagneticwaves can affect or corrupt data transfer.

To prevent interference with the data

transfer, the two data bus lines are twistedtogether. This also prevents noise emissionfrom the data bus line.

The voltage on both lines is opposed.

That means:

If a voltage of approximately 0 Volts isapplied to one data bus line, then a voltage

of approximately 5 Volts is applied to theother line and vice versa.

As a result, the total voltage remainsconstant at all times and theelectromagnetic field effects of the twodata bus lines cancel each other out.

The data bus line is protected againstreceived radiation and is virtually neutral insending radiation.

SSP 186/28

Approximately 0 Volts

SSP 186/29

Approximately 5 Volts


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10 ms 10 ms 10 ms

CAN Data Bus in the Drive Train

The features of the CAN Data Busin the drive train

The data bus comprises two linesalong which informaton is transferred.

In order to avoid electromagneticinterference and radiation emission,the two data bus lines are twistedtogether. Note the twist length.

The data bus operates at a speed of

500 kbit/s (500,000 bits per second).This means that it lies in a speed range(high speed) from 125 - 1000 kbit/s.A data protocol transfer takesapproximately 0.25 milliseconds.

Each control module (depending ontype) tries to send its data at intervalsof 7 - 20 milliseconds.

Order of priority:1. ABS Control Module (w/EDL)2. Motronic Engine Control Module (ECM)3. Transmission Control Module (TCM)

In the drive train, it must be possible totransfer the data very quickly so that it can

be fully utilized.For this purpose, a high-performancetransceiver is required.

This transceiver facilitates data transferbetween two ignition systems.This means that the received data can beused for the next ignition impulse.

SSP 186/22

SSP 186/24

SSP 186/23

SSP 186/38

SSP 186/25


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The Information in the Drive Train

What information is transferred?

The information transferred is veryimportant for the tasks of the individualcontrol modules. For example, the ABSControl Module (w/EDL) may needinformation for reasons of safety. TheEngine Control Module (ECM) needs

In the table below you can find examplesof the format of an individual item ofinformation. On account of the sheernumber of items of information which haveto be transferred, only one part is displayed.

The current position of the throttle valve istransferred with 8 bits, giving a possible256 bit permutations.Thus, throttle valve positions from 0 to102 can be transferred at 0.4 intervals.

information for controlling ignition timingand fuel injection quantity. TheTransmission Control Module (TCM)needs information for reasons of drivingconvenience and shifting comfort.

Bit Order Throttle Valve Position

0000 0000 000.0 Throttle valve opening angle





Order of Data Protocol Form Examples of InformationPriority

1 ABS Control Module (w/EDL) - Request for engine braking control (EBC)- Request for Traction Control System (TCS)

2 Engine Control Module (ECM), data - Engine speedprotocol 1 - Throttle valve position

- Kickdown

3 Engine Control Module (ECM), data - Coolant temperatureprotocol 2 - Vehicle speed

4 Transmission Control Module (TCM) - Gearshift- Transmission in emergency mode- Selector lever position



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Networking of the ControlModules in the Drive Train

J104 ABS Control Module (w/EDL)J217 Transmission Control Module

(TCM)J220 Motronic Engine Control Module

(ECM)

In contrast to the convenience system,only a part of the overall system isdisplayed in the drive train.In this case, only the networking of thecontrol modules is shown.

The node is usually located outside thecontrol module (in the wiring harness).

In exceptional cases, the node may belocated in the Engine Control Module(ECM).In the illustration below, you can see thenode at which the wires in the EngineControl Module (ECM) converge.

SSP 186/43

ABS Control Module(w/EDL)

Motronic EngineControl Module(ECM)

TransmissionControl Module(TCM)

CAN Data Bus (With Node in MotronicEngine Control Module (ECM)) SSP 186/39

SSP 186/34

J217 J104

J220

Node


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Self-Diagnosis of the CAN DataBus in the Drive Train

Self-diagnosis can be performed withthe V.A.G. 1551/52 or VAS 5051 underthese address words:

01 for engine electronics02 for transmission electronics03 for ABS electronics

SSP 186/42

VAS 5051

SSP 186/35

SSP 186/36

SSP 186/37

Data Bus Terminal

Data Bus Terminal

All control modules whichinterchange information must beregarded as an integrated systemduring self-diagnosis andtroubleshooting.

Th following function is relevant to theCAN data bus:

Function 02 - Interrogate fault memory

A fault is stored in the control modulesif data transfer between the controlmodules is disturbed:

Open circuit in one or more data buslines.

Short circuit between data bus lines.

Short circuit to ground or positive in adata bus line.

One or more control modules aredefective.


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Notes


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CAN Data Bus in the Convenience System

Future Use of the CAN Data Busin the Convenience System

In the future, the CAN data bus will be usedto connect the individual control modules ofthe convenience system.

These are: A central control module and Two or four door control modules

The structure of the CAN data bus in theconvenience system

The lines of the control modules convergeat one point in a star pattern. Theadvantage: if one of the control modulesfails, the other control modules are still ableto send their data protocols.

The following functions of the conveniencesystem transfer data:

Central locking Electric windows Switch illumination Electrically adjustable and heated

door mirrors Self-diagnosis

SSP 186/21

What are the advantages of the CANdata bus in the convenience system?

Fewer lines are routed via the doorconnections.

In the event of a short circuit to ground,to positive or between lines, the CANdata bus goes to emergency runningmode and changes over to single-wiremode.

Fewer diagnosis lines are required,because self-diagnosis is handledentirely by the central control module.


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The Features of the CAN Data Busin the Convenience System

The data bus comprises two linesalong which information is sent.

To avoid electromagnetic interferenceand radiation emission, the two databus lines are twisted together.

The data bus operates at a speed of62.5 kbit/s (62500 bits per second). This

means that it lies in a speed range(low speed) from 0 - 125 kbit/s. A dataprotocol transfer takes approximately1 millisecond.

Each control module tries to send itsdata at intervals of 20 milleseconds.

Order of priority:1. Central control module2. Control module on drivers side3. Control module on front passengers side4. Control module on rear left5. Control module on rear right

Since the data in the comfort system canbe transferred at a relatively low speed, it ispossible to use a transceiver with a lowerpower output.

The advantage is that it is possible tochange over to single-wire mode if a databus line fails. The data can still betransferred.

SSP 186/22

SSP 186/24

SSP 186/23

SSP 186/25

SSP 186/26

20 ms 20 ms 20 ms

1 2

34

5


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Information in the ConvenienceSystem

The information relates to states of theindividual functions.For example, information about whichradio-wave remote control was operated,current status of central locking, do errorsexist, and so on.

The table shows you part of the data fieldof the drivers door control module by wayof an example.

Example showing a possible bit order

You can see how and what informationregarding the status of the central lockingand the electric windows is transferred.

SSP 186/27

1 = 5 Volts

0 = 0 Volts

Bit 5 Bit 4 Bit 3 Bit 2 Bit 1

Function Information Bit Order Value ofStatus Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 BitsCentral Basic status 0 Volts, 0 Volts, 0 Volts 000locking Safe 0 Volts, 0 Volts, 5 Volts 001

Locked 0 Volts, 5 Volts, 0 Volts 010Door unlocked 0 Volts, 5 Volts, 5 Volts 011The central locking is unlocked 5 Volts, 0 Volts, 5 Volts 101Door locked 5 Volts, 0 Volts, 0 Volts 100Signal error, input sensors 5 Volts, 5 Volts, 0 Volts 110Status error 5 Volts, 5 Volts, 5 Volts 111

Electric In motion 0 Volts, 0 Volts 00

windows Not moving 0 Volts, 5 Volts 01Within range 5 Volts, 0 Volts 10Upper stop recognized 5 Volts, 5 Volts 11

Bit Order Value Voltage Applied to Meaning of InformationData Bus Line

3 to 1 101 5 Volts, 0 Volts, 5 Volts The central locking is unlocked

5 to 4 10 5 Volts, 0 Volts The window is located in the zone between the upper stop(completely closed) and 4 mm below the window seal


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Networking of Control Units inthe Convenience System

Control Units:

J386 Door control module, driver side

J387 Door control module, passenger side

J388 Door control module, rear left

J389 Door control module, rear right

J393 Central control module for comfortsystem

Fuses:

S6 Fuse, terminal 15 - central control moduleS14 Fuse, terminal 30 - central control moduleS37 Power Window Fuse, terminal 30S238 Fuse, terminal 30 - central locking

Color Coding:

Input Signal

Output Signal

Positive

Ground

Data Bus Line High/Low

SSP 186/30

S37 S238

J386

J386

31

3015X

31


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J393 S6 S14

KJ387

J389

3015X

31

31


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The Self-Diagnosis of the CANData Bus in the ConvenienceSystem

Self-diagnosis is performed with V.A.G.1551/52 or with VAS 5051 underthe following address word:

46 Convenience system

During self-diagnosis andtroubleshooting, all controlmodules which interchangeinformation with the CAN data

bus must be regarded as anintegrated system.

The following functions are relevant to theCAN data bus:

Function 02 - Interrogate fault memory

In the fault memory, two faults areindicated specially for the CAN data bus.

Convenience data busThis fault is set if data transfer betweentwo or more control units fails.

Possible fault causes are: Defective control modules Open circuit in both data bus lines or

in plug and socket connections

Convenience data bus in emergency

running modeThis fault is indicated if the CAN data bushas entered emergency mode.

Possible fault causes are: Open circuit in one data bus line or

in a plug and socket connection

SSP 186/42

SSP 186/40

SSP 186/40

VAS 5051

Printout on

V.A.G. 1551 printer 01329

Convenience data bus inemergency running mode

Printout onV.A.G. 1551 printer

01328

Convenience data bus


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Function 08 - Read measured value block

Display group number 012 - Central

control unit - displays four display fieldsrelevant to the data bus.

Display field 1: Check busThis field indicates whether the data bus isOK or faulty (e.g. fault in single wire).

Display field 2: Equipment frontThis field indicates which front controlmodules are installed and participate in datatransfer.

Display field 3: Equipment rearThis field indicates which rear controlmodules are installed and participate in datatransfer.

Display field 4: AccessoriesThis field indicates whether the seat andmirror adjustment memory system isinstalled. Both systems (conveniencesystem and memory system) interchange

data.

Direct CAN data transfercurrently cannot be checkedusing the available workshopfacilities.

SSP 186/41

Display Group 012 - Central Control Unit

Read measured value block 12 Display on monitor

Display fields Setpointxxx xxx xxx xxx

1 2 3 4Accessories

Equipment rear

Equipment front

Check Bus

Memory / empty 1)

RLRL and RR

RRempty 1)

DriverDriver and FP

FPempty 1)

Bus OKBus NOK


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Notes


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Knowledge Assessment

An on-line Knowledge Assessment (exam) is available for this SSP.

The Knowledge Assessment may or may not be required for Certication.

You can nd this Knowledge Assessment at:

www.accessaudi.com

From the accessaudi.com homepage:

Click on the ACADEMY Tab

Click on the Academy Site Link

Click on the CRC Certication Link

For assistance, please call:

Audi Academy

Learning Management Center Headquarters

1-877-AUDI-LMC (283-4562)

(8:00 a.m. to 8:00 p.m. EST)

Knowledge Assessment

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Audi CAN Data Bus