Audi Workshop Service and Repair Manuals

Note:

The signal wire between immobiliser control unit and Motronic control unit is used both as a data wire between the control units as well as for data transfer of engine self-diagnosis.

If the engine starts briefly and then cuts out again, the following faults are possible:

• ● Engine control unit inhibited by signal from immobiliser control unit.
• ● Open circuit in signal wire from immobiliser control unit to Motronic control unit or short circuit to positive or ground.

• ‒ Interrogate fault memory =>Page 01-8.

If the fault "17978, engine control unit inhibited" is displayed, there is no fault in the wiring connection. Eliminate the cause for the inhibition through the immobiliser.

=> Electrical System; Repair Group 01; Immobiliser Self-diagnosis; 02 Interrogating fault memory

• ‒ If the engine electronics cannot be called up because a fault is displayed in the communications build-up, then select the immobiliser with address word 25.

• ‒ If a fault is displayed again in the communications build-up, test the diagnostic wire - see Fault-finding program for diagnostic wires.

=> Current Flow Diagrams, Electrical Fault-Finding and Fitting Locations

• ‒ → If the immobiliser control unit sends a message then connect test box V.A.G 1598/19 at the wiring harness for the Motronic control unit.

• ‒ → Test wiring connection from contact A7 at the Motronic control unit ...

• ‒ → ... to contact 9 on the immobiliser control unit for continuity and short to positive or ground and repair as necessary.