Checking ignition retardation during gear selection: VW (ADP, AJH)

Vehicles with automatic gearbox only

The engine control unit receives the gear selection signal via the gearbox control unit. The engine then, depending on road and engine speeds, retards the ignition briefly. This reduces the torque and gear jolt.

The V.A.G 1551 does not always recognise and display the signal for torque reduction because it is sent for an extremely short period.

Note:

To check the ignition retardation the vehicle must be driven. To do this a second person is necessary.

Warning!
Secure fault reader to rear seat and operate from this position.
Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
Test box V.A.G 1598/22
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Current flow diagram

Test sequence

Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
(Connecting fault reader and selecting engine control unit => Page
01-5
.)

Rapid data transfer
HELP
Select function XX
Indicated on display:

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

Read measured value block
HELP
Input display group number XXX
Indicated on display:

Press keys 0, 1 and 9 for "Display group number 19" and confirm entry with Q key.

Read measured value block 19
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Observe figure displayed in display zone 3:
(3rd digit from left)
Specification: _x 1 _ _ _ _ x
Carry out test drive with a 2nd person to observe display.
Observe figure displayed in display zone 3. Whilst selecting a gear the display in display zone 3 (3rd digit from left) must briefly display
Specification: _x 0 _ _ _ _ x

Note:

It is possible that several gear changes must be performed before the display in display zone 3 jumps to 0 as the signal from the automatic gearbox is very brief.

Press the ⇒key.
Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
Switch off ignition.

If the display does not change:

Connect test box V.A.G 1598/22 to control unit wiring harness.
Check wiring between test box sockets 29 and 41 and automatic gearbox for open circuit according to current flow diagram.
Wire resistance: Max. 1.5 ω