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Resistance in wiring: max. 1.5 ω
- Rectify any open/short circuit as necessary.
- If there are no faults in the wiring, test operation of air conditioner.
=> Air conditioner; Repair Group 01; Self-diagnosis for air conditioner Self-diagnosis for air conditioner
8.4 - Testing data exchange between control units
Notes:
◆ The data exchange between the various control units is carried out via a data bus.
◆ The term "CAN data bus" refers to a system for transmitting and distributing data.
◆ The wires which connect the control units and convey the data between them are called data wires.
◆ Data is transmitted via data wires in sequence, i.e. in a specific order to the connected control units (e.g.
engine rpm and accelerator pedal position).
Testing bus system
If the fault table instructs you to test the data exchange between the engine control unit, ABS control unit,
gearbox control unit and/or dash panel insert:
- Check that multi-pin connectors for control units are properly seated.
- Connect vehicle diagnostic, testing and information system VAS 5051 (or fault reader V.A.G 1551) and
select engine electronics control unit by entering address word "01" ( => Page
When doing this the engine must be idling.
-> Indicated on display:
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.
-> Indicated on display:
Read measured value block
Enter display group number XXX
- Press keys 1, 2 and 5 to select "Display Group 125" and confirm entry with Q key.
-> Indicated on display:
Read measured value block 125
1 2 3 4
Display zones
1
2
3
4
Display group 125: CAN data bus messages with ignition on
Display
Gear. 1
ABS 1
Indicates
CAN data bus
(gearbox control unit)
CAN data bus
(ABS control unit)
Range
1 = OK
0 = not OK
1 = OK
0 = not OK
Specification
Gear. 1
ABS 1
Note
If specification is not obtained for one or more control units, perform automatic test sequence.
- Press key 0 twice for address word "Automatic test sequence" and confirm entry with Q key. The V.A.G
1551 transmits all known address words one after the other.
Audi A8 1994 ➤
Motronic injection and ignition system (6-cylinder) - Edition 02.1999
90
24 - Mixture preparation, Injection
