Audi Workshop Service and Repair Manuals

The speed signal is required for shutting off the air conditioner compressor when accelerating, for the cruise control system and to ensure smoother driving (jolt damping).

Test conditions

• ● Speedometer OK, checking:

=> Electrical System; Repair group 90

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select the engine electronics control unit using "Address word" 01. When doing this the engine must be running at idling speed.
  (Connecting fault reader and selecting engine electronics control unit .)

• ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

• ‒ Press keys 0, 0 and 6 for "display group number 6" and confirm entry with Q key.

• ‒ Carry out a test run and compare the display on display 2 (2nd person required) with the display on the tachometer.

• ‒ Observe readout in display zone 1.

If specified value is not attained:

• ‒ Connect test box V.A.G 1598/22 to wiring harness for engine control unit .

The following wiring connections are to be checked for open circuits and/or short to positive or negative.

• ‒ Rectify any open/short circuit as necessary.

If no wiring fault is detected:

• ‒ Find all the speed signal "consumers" (e.g. radio, automatic gearbox, air conditioner etc.), disconnect them one by one from the dash panel insert, then repeating the test until the cause of the problem has been identified.