Component Tests and General Diagnostics

Control Module Voltage Supply Check

Special tools and equipment
- Scan tool VAG 1551 or vehicle system tester VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/31
- 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.







- Fuses 10 and 29 must be OK.
- Alternator OK, checking:

Test sequence
- Connect scan tool VAG 1551 (VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this the engine must be running at idling speed.

(Connecting scan tool and selecting engine control module). Refer to "VAG 1551 Scan Tool" [1][2][3][4][5]Connecting VAG 1551 Scan Tool

Indicated on display:


Rapid data transfer HELP
Select function XX


- Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Indicated on display:


Read measured 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: (1-4 = Display zones)


Read measured value block 4 ->
1 2 3 4


- Read off figure displayed in display zone 2.
Specification: At least 11.5 V
- Press the -> key.
- Press keys 0 and 6 for the "End data transfer" function and confirm input with the -Q- key.
- Switch off ignition.

If the specification is not attained:







- Connect test box VAG 1598/31 to control module wiring harness. The engine control module remains disconnected.

Checking voltage supply terminal 30
- Measure supply voltage between test box sockets 1 + 62 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 with multimeter and aux. cables from VAG 1594 between test box sockets 2 and 3:
- Switch on ignition.
Specification: min. 11.5 V

If the specification is not attained:
- Check wiring connections to relay plate according to wiring diagram.

Checking voltage supply via main relay
- Measure voltage supply between sockets 2 + 121 of test box using multimeter and adapter cables from VAG1594 connector test kit:
- Switch on ignition.
Specification: min. 11.5 V


NOTE: Voltage supply is maintained for several minutes even after ignition is switched off.


If the specification is not attained:
- Check wiring connections to relay plate according to wiring diagram.
- Check activation wire from Engine Control Module (ECM) terminal 21 to Motronic Engine Control Module (ECM) power supply relay -J271- according to wiring diagram.