Component Tests and General Diagnostics
Engine Control Module (ECM) Voltage Supply, Checking
Special tools and equipment
- VAG 1551 Scan Tool or VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/22
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram
Check conditions
- The battery voltage must be at least 11.5 V.
- Alternator OK, checking
Test sequence
- Connect VAG 1551 Scan Tool ((VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this engine must be running at idle speed. (Connecting scan tool and selecting engine control module [1][2][3]Connecting VAG Scan Tool 1551/1552).
Indicated on display
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for function "Read Measuring Value Block" and confirm entry with Q key.
Indicated on display
Read Measuring Value Block HELP
Input display group number XXX
- Press keys 0, 0 and 4 for "Display group number 4" and confirm entry with Q key.
Indicated on display: (1 to 4 = Display zones)
Read Measuring Value Block 4 ->
1 2 3 4
- Read off figure displayed in display zone 2.
Specification: At least 11.5 V
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
If the specification is not attained:
- Connect test box VAG 1598/22 to control module wiring harness.
Checking voltage supply terminal 30
- Measure supply voltage between test box sockets 2 + 3 using multimeter and adapter cables from VAG 1594:
- Specification: at least 11.5 V
If the specification is not attained:
- Check wiring connections to relay plate according to wiring diagram.
Checking voltage supply terminal 15
- Measure supply voltage between test box sockets 1 + 2 using multimeter and cables from VAG 1594.
- Switch ignition on.
- Specification: min. 11.5 V
If the specification is not attained:
- Check wiring connections to relay plate according to wiring diagram.
Checking voltage supply terminal 15
- Measure supply voltage between test box sockets 1 + 2 using multimeter and cables from VAG 1594.
- Switch ignition on.
- Specification: min. 11.5 V
If the specification is not attained:
- Check wiring connections to relay plate according to wiring diagram.
Procedure after voltage supply open circuit
All values learned by the engine control module and the basic setting values as well as the readiness code will be erased if the voltage supply is interrupted. Therefore, depending upon the vehicle mileage it can lead to serious engine running problems.
Special tools and equipment
- VAG 1551 Scan Tool or VAG 1552 with cable VAG 1551/3
Work sequence
Perform the following operations after voltage supply open circuit:
- Switch ignition on for at least 10 seconds.
- Switch ignition off.
- Perform idle speed check Testing and Inspection.
NOTE: During idle speed check the EVAP canister purge regulator valve and the air conditioner are switched off and the Oxygen sensor control learning procedure is initiated.
- Perform a longer test drive until poor driving characteristics are eliminated.
During the road test the following operating conditions must be fulfilled:
- The coolant temperature must exceed 80 degree C.
- When the temperature is reached, the operating conditions
Idling
Part throttle
Wide open throttle
Overrun
must be attained several times.
- At wide open throttle the speed must exceed 3500 RPM.