With Manufacturer Scan Tool

Heated Oxygen Sensor (HO2S) For Oxygen Sensor After Catalyst, Checking


Special tools and equipment
- Scan tool VAG 1551 or vehicle system tester V.A.G 1552 with cable VAG 1551/3B
- Test box V.A.G 1598/31
- Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
- Adapter set V.A.G 1594
- Wiring diagram

Check conditions







- All fuses 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 (V.A.G 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. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1551 Scan Tool" Testing and Inspection

Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons 0 and 8 for function "Read Measuring Value Block" and confirm entry with Q button.

Indicated on display


Read Measuring Value Block
Input display group number XXX


- Press buttons 0, 4 and 1 for "Display group number 41" and confirm entry with Q button.

Indicated on display (1-4 = Display zones)


Read Measuring Value Block 41 ->
1 2 3 4


- Let engine run 2 minutes at idle speed.
- Check status of heated oxygen sensor behind catalyst in display field 4.
Display: Htg.bC.ON, Htg.aC.OFF (alternating)

If the specification is obtained:
- Press -> button.
- Press buttons 0 and 6 for function "End output" and confirm entry with Q button.
- Switch ignition off.

If the specifications are not obtained:
- Press-> button.
- Press buttons 0 and 6 for function "End output" and confirm entry with Q button.
- Switch ignition off.







- Remove protective cover -arrows- and separate 4-pin connector (brown) -1- to oxygen sensor after catalyst (G130).







- Set multimeter to measure resistance and check sensor heating resistance at connector to oxygen sensor terminals 1 + 2. Check oxygen sensor heating for continuity.

If an open circuit is detected in the oxygen sensor heating:
- Replace oxygen sensor after catalyst (G130).
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory. Refer to "Displaying and Reading Trouble Codes/With Manufacturers Scan Tool/DTC Memory Checking and Erasing" Testing and Inspection

If the oxygen sensor heating has continuity:







- Set multimeter to measure voltage and connect to terminal / (connector to engine control module) and Ground.
- Start engine and run at idle speed.
- Measure voltage supply:
Specification: 11.0 to 14.5 V

If the specification is not obtained:
- Check wiring between terminal 1 and fuel pump relay (J17) using wiring diagram.

Checking voltage supply







- Connect multimeter using auxiliary cables from VAG 1594 to measure voltage at terminals 1 + 2 (connector to engine control module).
- Start engine and run at idle speed.
- Measure voltage supply and observe display group 41, display zone 4.
Display: Htg.aC.ON:
- Specification: 11.0-14.5 V

Display: Htg. aC.ON/Htg.aC.OFF (alternating):
- Specification: Between 0.0-12.0 V fluctuating

- Switch ignition off.

If no voltage is present:
- Remove inner plenum chamber cover, left:






- Connect test box V.A.G 1598/31 to control module wiring harness. Engine control module is not connected by this action.







- Check wiring for open circuit between test box and 4-pin connector according to wiring diagram.
Terminal 2 + socket 63:
- Wire resistance: Max. 1.5 Ohms


If the specification is obtained:

If there is no malfunction in the wiring:
- Replace Engine Control (ECM).