Ignition Timing: Testing and Inspection
Timing Control During Shifting, Checking
NOTE:
- When shifting the automatic transmission, this signal from the Transmission Control Module (TCM) retards the ignition timing briefly, depending on vehicle speed and engine RPM (reduction of torque), to reduce shift pressure.
- Because of the very brief signal to reduce torque, the signal is not always recognized by the VAG 1551 scan tool, and therefore is not always indicated.
Required special tools and test equipment
- VAG 1551 or VAG 1552 Scan Tool (ST) with VAG 1551/3 adapter cable
- VAG 1598/22 test box
Test procedure
- Connect VAG 1551 or VAG 1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle) See page 01-7.
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
- Press buttons 1, 2 and 2- to input display group number 122, and press -Q- button to confirm input.
Indicated on display (1-4 = display fields)
Read Measuring Value Block 122 ->
1 2 3 4
- Road test.
WARNING!
A second technician is required to operate the VAG 1551 scan tool during the road test
- Compare display with specified value in display field 4:
Display Group 122:
If display is OK (as specified):
- Press -> button to advance program sequence.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
Continuation
NOTE: The wiring to the Transmission Control Module is monitored by On Board Diagnostic and stores the Diagnostic Trouble Code 00545 if there is a malfunction.
If displayed value is NOT OK (not as specified), or if DTC 00545 is stored in DTC memory:
- Connect VAG 1598/22 test box to ECM harness connector See page 01-55.
- Check wiring for short circuit or open circuit between ECM harness connector terminal 23 and to Transmission Control Module (TCM), according to wiring diagram