Ignition Retardation During Gear Shifts, Checking

Ignition retardation during gear shifts, checking

The engine control module (ECM) receives the gear shift signal via the Transmission Control Module (TCM). Depending on road and engine speeds the ECM retards the ignition briefly. This reduces engine torque to prevent harsh gear shifts.

The VAG1551 scan tool does not always recognize and display the signal for torque reduction (ignition retardation) because it is sent for an extremely short period of time.

NOTE: To check the ignition retardation the vehicle must be driven. To do this a second technician is needed to observe the display on the scan tool.

WARNING!
- When driving or riding in an airbagequipped vehicle, NEVER hold the scan tool or other test equipment in your hands or lap while in motion. Objects between you and the airbag increase the risk of injury in an accident.
- During a test drive in an airbag-equipped vehicle, test equipment must always be fastened to and operated from the rear seat by a second technician.

Special tools and equipment
- VAG1551 or VAG1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter US1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- Wiring diagrams

Checking
- Connect VAG1551 or VAG1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle), Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1551/VAG1552 Scan Tool" under "Engine", Testing and Inspection

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

NOTE: It is possible that several gear shifts must be performed before the display in display field 3 jumps to 0 as the signal from the automatic Transmission Control Module (TCM) is very brief.

- Press buttons -1-, -2-and -2-to input display group number 122 (122), and press -Q- button to confirm input.

Indicated on display (1-4 = display fields)

Read Measuring Value Block 122 ->
1 2 3 4

- Carry out test drive with second technician to observe display.
- Check specifications in display field 4.






If the specification is attained:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Check readiness code. If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If the display does not change:






- Connect VAG1598/22 test box to ECM harness connector.
- Check wiring for open circuit between ECM/test box (sockets 29 and 41) and TCM using appropriate wiring diagram.
- Specified value: max. 1.5 Ohms

If the wiring is OK:
- Replace TCM -J217

If the display does not change again after replacing the TCM:
- Replace Motronic ECM -J220-.