Oxygen Sensor Heating, Checking

Oxygen sensor heating, checking

NOTE: The oxygen sensor heating circuit is monitored by the On Board Diagnostic (OBD) system, checking Diagnostic Trouble Code (DTC) memory.

- Connect vehicle diagnostic, testing and information system VAS 5051 or VAG 1551 Scan Tool and select engine electronics control module 1 with "Address word" 01. For this purpose, engine must be running at idle speed.
Connecting VAS 5051 Scan Tool
[1][2]Scan Tool Connecting and Initial Checks

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 08
Enter display group number XXX


- Press keys 0, 4 and 1 for "display group number 41" and confirm entry with Q key.

Indicated on display


Read measured value block 41 ->
1 2 3 4


- Check resistance of oxygen sensor heating.

Display Group 41:

- Press Ckey.
- Press keys 0, 4 and 2 for "display group number 42" and confirm entry with Q key.

Display Group 42:

If specified value is not attained:
- Check voltage supply to oxygen sensor heating.
- Check oxygen sensor signal wiring and actuation Oxygen Sensor Signal Wiring and Actuation, Checking

Checking voltage supply for oxygen sensor heating

Installation locations of 4-pin connectors for oxygen sensors.
- Check fuse for oxygen sensor heating.
- Disconnect 4-pin connector of relevant oxygen sensor.







- Using leads from VAG 1594, connect hand-held multimeter (voltage measurement range) to sockets 1 (positive) and 2 (Ground).
- Operate starter briefly.

Specified value: approx. battery voltage

If no voltage is present:







- Using leads from VAG 1594, connect hand-held multimeter (voltage measurement range) to socket 1 (positive) and vehicle Ground.
- Operate starter briefly.

Specified value: approx. battery voltage

If no voltage is present:
- Check wiring from socket 1 of relevant oxygen sensor connector on wiring harness via fuse to fuel pump relay for open circuit or short.

If the power supply is OK:







- Using leads from VAG 1594, connect hand-held multimeter (voltage measurement range) to socket 2 (Ground actuation from engine control module) and battery positive.
- Start engine.

Specified value: approx. battery voltage, fluctuating

NOTE: At certain operating points, the engine control module "cycles" the Ground for the oxygen sensor heating. This means that at these points, the Ground is continuously switched on and off. For this reason, the voltage reading on the tester may fluctuate.

- Switch ignition off.

If no voltage is present:
- Connect test box V.A.G 1598/31 to wiring harness for engine control module; do not connect engine control module. Connecting VAG 1598/31 Test Box







- Check for open circuit in following wiring connections:

Heated Oxygen Sensor (HO2S) -G39-

Connector on wiring
harness, socket Test box V.A.G 1598/31 socket
2 5 (Ground)

Heated Oxygen Sensor (HO2S) 2 -G108-

Connector on
wiring harness, socket Test box VAG 1598/31 socket

2 4 (Ground)

Oxygen Sensor (O2S) behind TWC -G130-

Connector on
wiring harness, socket Test box VAG 1598/31 socket

2 63 (Ground)

Oxygen Sensor (O2S) 2 behind TWC -G131-

Connector on wiring
harness, socket Test box VAG 1598/31 socket

2 6 (Ground)

Wire resistance: max. 1.5 Ohm

If wiring connections are OK:
- Replace appropriate oxygen sensor.
- Read readiness code. Generate readiness code again if DTC memory was erased. Readiness Code, Generating