Checking wiring to gearbox control unit: Audi 2.5 TDI (AAT, ABP, AEL)

ABP AEL
Special tools and workshop equipment required

V.A.G 1526 A
V.A.G 1527 B
V.A.G 1594 A
V.A.G 1598 with V.A.G 1598/5

A - Signal for gearshift

Notes:

Perform the following test only if fault 00545: "Engine/gearbox electrical connection" is indicated.
This signal briefly retards the ignition timing on changing gear to reduce gearshift jolt.

With ignition switched off, use adapter V.A.G 1598/5 to connect test box V.A.G 1598 A to engine control unit connector and also to actual engine control unit => Page
23-45
.
Connect up voltage tester V.A.G. 1527 B between sockets 18 (earth) and 43 (signal) on test box.
Switch on ignition.
LED must light

If LED lights:

Perform the dynamic test => Page
23-161
.

If LED does not light:

Unplug connector from gearbox control unit.

=> Automatic Gearbox; Repair Group 37
Automatic Gearbox

If LED now lights:

Find fault in gearbox control unit.

If LED still does not light:

Use current flow diagram to check wiring between engine control unit and gearbox control unit for shorting.-

If no fault is found in wiring:

Replace engine control unit => Page
23-48
.

Dynamic testing

Attention:
To avoid risk of accident when performing measurement and test drives, pay attention to safety precautions => Page
23-1
.
Perform test drive.
The LED must go out briefly during gear shifting.

If LED does not go out:

Use current flow diagram to check wiring between engine control unit and gearbox control unit for open circuit or short to positive.

If no fault is found in wiring:

Find fault in gearbox control unit.

B - Signal for accelerator pedal position

Notes:

Perform the following test only if fault 00638: "Engine/gearbox electrical connection 2" is indicated.
This signal is required for load-dependent calculation of the shift points.

With ignition switched off, use adapter V.A.G 1598/5 to connect test box V.A.G 1598 A to engine control unit connector and also to actual engine control unit => Page
23-45
.
Connect up multimeter to measure voltage between contacts 18 (earth) and 40 (signal) on test box.

Switch on ignition.
Specification: 0.4 ... 0.8 V

Slowly floor accelerator pedal.
Specification: Steadily rising up to 8.5 ... 10 V

If readout is not as described:

Unplug connector from gearbox control unit.

=> Automatic Gearbox; Repair Group 37
Automatic Gearbox

If readings now match specifications:

Find fault in gearbox control unit.

If readings still do not match specifications:

Use current flow diagram to check wiring between engine control unit and gearbox control unit for open circuit or short to positive.

If no fault is found in wiring:

Check accelerator pedal position sender => Page
23-124
.

If accelerator pedal sender is OK:

Replace engine control unit => Page
23-48
.

C - Signal for engine speed

Notes:

Perform the following test only if fault 00529: "Engine speed information, engine speed" is indicated.
This signal is required to calculate the gear shift comfort.

Perform the signal test=>Checking engine speed signal, Page
23-153
.

D - Signal for engine torque

Notes:

Perform the following test only if fault 00549: "Consumption signal" is indicated.
This signal is required to calculate the gear shift comfort.

Perform the signal test => Checking consumption signal for on-board computer, Page
23-156
.