Audi Workshop Service and Repair Manuals

Notes:

• ◆ The engine control unit receives the gearshift signal from the gearbox control unit. (If the control unit has a CAN bus, the signal is transmitted via the CAN bus data wire.) The engine control unit then retards the ignition timing briefly according to the road speed and engine speed. This reduces the torque and thus ensures a smoother gear change.
• ◆ Because the signal is very brief, fault reader V.A.G 1551 does not always register the instruction to reduce the torque, and therefore this may not be shown on the display.

Special tools, testers and auxiliary items

• ◆ Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with cable V.A.G 1551/3

• ‒ Connect fault reader V.A.G 1551
  .
• ‒ Start the engine.
• ‒ Select "Read measured value block", Display Group 019, engine at idling speed.

• ‒ Pull handbrake fully on and additionally depress the foot brake.
• ‒ Observe displays in the display zones 3 and 4 when selecting a gear.
• ‒ Display zone 3 displays the required engine torque for gear selection (specified torque).
• ‒ Display zone 4 displays the actual engine torque (clutch torque/actual torque).

• When a gear is engaged the readouts in the two display zones should match. The ignition timing retardation is now activated.

• ‒ If the ignition timing retardation is not activated, continue the test as follows:

Vehicles with engine control unit numbers

up to 4D0 907 551 F

The gearshift signal and the signal wire are monitored by the gearbox self-diagnosis (fault code 00545).

=> Automatic gearbox 01V - Self-diagnosis; Repair group 01; Performing self-diagnosis

• ‒ → If the measured value block does not indicate any torque reduction during the gearshift, or if the gearbox control unit has stored fault code 00545, connect test box V.A.G 1598/22 to the wiring harness for the engine control unit.
• ‒ Test for open circuit and short circuit in wiring from engine control unit to gearbox control unit using the current flow diagram.

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

Vehicles with engine control unit numbers

from 4D0 907 551 G onwards

The engine control unit and gearbox control unit exchange data via the CAN bus.
=>Testing CAN bus, Page 24-121.