Audi Workshop Service and Repair Manuals

Notes:

• ◆ This signal is produced by the automatic gearbox control unit during a gearshift. The signal enables the ignition timing to be briefly retarded by varying amounts (torque reduction) depending on the road speed and engine speed. This smooths out the slight jerk as the gear engages.
• ◆ The signal is a square wave signal which is fed to contact 23 on the engine control unit.
• ◆ Because the signal is very brief the V.A.G. 1551 does not always recognise the command to retard the ignition timing.

• ‒ Connect fault reader V.A.G 1551 .
• ‒ Take the vehicle for a test drive and select "Read measured value block" (function 08) and Display Group 1 => Page 01-85.

Readout: X 0 X X X X X X = without gearshift

Readout: X 1 X X X X X X = with gearshift

Value: X = (no meaning)

Note:

When the gearbox control unit gives the command for the ignition timing to be retarded the readout will change briefly from "0" to "1".

• ‒ The wiring connection to the gearbox control unit is monitored by the gearbox self-diagnosis (fault code 00545).
• ‒ → When changing gear, if the measured value block does not indicate that a reduction in torque is required, or if fault code 00545 appears (gearbox control unit), connect test box V.A.G 1598/22 to the wiring harness for the engine control unit.
  => Page 24-13
• ‒ Test for open circuit or short to positive or earth in wiring between gearbox control unit and contact 23 on the engine control unit.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder