Ignition Timing: Testing and Inspection
Ignition Retarding During Transmission Range Selection, Checking
The Engine Control Module (ECM) receives the Transmission Range signal via the Transmission Control Module (TCM). The ECM then, depending on vehicle and engine speeds, briefly retards the ignition, thus reducing torque and therefore shift jolt.
The VAG 1551 does not always recognize and display the torque reduction signal because it only exists for a fraction of a second.
NOTE: The vehicle must be driven to check ignition retarding and requires the assistance of a second technician.
Observe the appropriate safety precautions during road test.
Special tools, workshop equipment, testers, measuring instruments and auxiliary items required
- VAG 1551/1552 Scan Tool using VAG 1551/3 Adaptor cable
- VAG 1598/22 Test Box
- Fluke 83 multimeter
- VW 1594 Adaptor kit
- Wiring diagram
Test sequence
- Connect VAG 1551/1552 Scan Tool. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks", Testing and Inspection
- Start engine and let idle
- Press 0 and 1 buttons to select "Engine Electronics" address word 01.
Indicated on display (example only)
06A906018AB Motronic M5.9.2 HS V06 ->
Coding 00000 WSC 00000
- Press -> button.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press 0 and 8 buttons to select "Read Measuring Value Block" function 08.
- Press Q button to enter input.
Indicated on display
Read measuring value block HELP
Input Display group number XXX
- Press 1, 2 and 2 buttons to select "Display group 122"
- Press Q button to enter input.
Indicated on display (1 to 4 = Display fields)
Read measuring value block 122 ->
1 2 3 4
- Take a test drive with a 2nd technician to observe display.
Observe the appropriate safety precautions during road test.
- Check specifications in Display field 4:
NOTE: It us possible that several Transmission Range changes must be performed before the value in Display field 3 jumps to 0 because the TCM Transmission Range signal duration is very brief.
If specification obtained
- Press the -> button.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press 0 and 6 buttons to select Function 06: "End output"
- Press Q button to enter input.
- Switch OFF ignition.
- Display the Readiness code. Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Displaying Readiness Code", Testing and Inspection
- If DTC memory was erased or if the ECM was disconnected from Battery + , set the Readiness code. Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Setting Readiness Code", Testing and Inspection
If display does not change
- Connect VAG 1598/22 Test Box to ECM wiring harness.
- Check wiring for open circuit between Test Box sockets 29 and 41 and the Transmission Control Module (TCM) using Wiring diagram.
- Wire resistance: 1.5 Ohms maximum
If wiring OK:
- Replace Transmission Control Module.
If malfunction still displayed after TCM is replaced
- Replace Engine Control Module.