With Manufacturer's Scan Tool

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







- Fuse 43 must be OK.
- The battery voltage must be at least 11.5 V.
- Fuel pump relay must be OK

Test sequence
- Connect scan tool VAG 1551 (VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this 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 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, 4 and 2 for "Display group number 42" and confirm entry with Q key.

Indicated on display: (1-4 = Display zones)


Read measured value block 41 ->
1 2 3 4


- Check status of heated oxygen sensor before catalyst in display zone 2:

Display: Htg.bC.ON


NOTE: The heated oxygen sensor may be switched on or off depending on the operating mode of the engine, therefore the display in display zone 2 may show "Htg.bC.ON or alternating from Htg.bC.ON to Htg.bC.OFF.


If the display does not indicate as described:







- Remove protective cover (arrows) and separate 4-pin connector (black) to Oxygen sensor before catalyst (G39).







- Check probe heating for continuity at Oxygen sensor connector contacts 1 and 2.

If it is determined that probe heating has an open circuit:
- Replace Oxygen sensor before catalyst (G39).

If probe heating has continuity:







- Set multimeter to measure voltage and connect to contacts 1 and 2 on connector to control module.
- Start engine and run at idling speed.
- Measure voltage supply:

When display group 41, display zone 2 displays: Display, Htg.bC.ON:

Specification: 11.0 - 14.5 V

Display, Htg.bC.ON/Htg.bC.OFF (alternating)

Specification: Between 0.0 - 12.0 V fluctuating

- Switch off ignition.

If no voltage is present:







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







- Check wiring between test box and 4-pin connector for open circuit according to wiring diagram.
Contact 2 + socket 5
Wire resistance: Max. 1.5 ohms

If the specification is obtained:
- Check wiring from contact 1 to fuel pump relay (J17) according to wiring diagram.