Oxygen Sensor Heating, Checking

Oxygen Sensor Heating, Checking

NOTE: The heating circuit for the oxygen sensors is monitored by the self-diagnosis function (interrogating fault memory).

Requirement
- Fuse for oxygen sensor heating OK

Work sequence
- Disconnect 4-pin connector to relevant oxygen sensor (refer to exploded view of component locations).







- Connect multimeter for resistance measurement between contacts 1 and 2.
- Specification at ambient temperature: 2.5 ... 15 Ohm

If reading does not match specification:
- Replace relevant oxygen sensor.

If reading matches specification:

Checking power supply for oxygen sensor heating

- Check fuse for oxygen sensor heating.
- Disconnect 4-pin connector of relevant oxygen sensor.







- Connect portable multimeter with test leads from V.A.G 1594 to sockets 1 (positive) and 2 (Ground) for voltage measurement.
- Briefly operate starter.
Specification: approx. battery voltage

NOTE:
- Activation and deactivation of oxygen sensor heating by the engine control module can be observed if necessary in the "Reading measured value block" function, display group number 041, display zones 2 and 4 for the oxygen sensors of cylinder bank 1. For the oxygen sensors of cylinder bank 2 the display group number is 042 (display zones 2 and 4).
- The terms "Upstream heating" and "Downstream heating" stand for "Heating upstream of catalytic converter" and "Heating downstream of catalytic converter" respectively.

If there is no voltage:







- Connect portable multimeter with test leads from V.A.G 1594 to socket 1 (positive) and vehicle Ground for voltage measurement.
- Briefly operate starter.
Specification: approx. battery voltage

If there is still no voltage:
- Check for open circuit/short circuit in wiring from socket 1 of relevant oxygen sensor connector at wiring harness via fuse to fuel pump relay.

If power supply is OK:







- Connect portable multimeter with test leads from V.A.G 1594 to socket 2 (engine control module switched Ground connection) and battery positive for voltage measurement.

- Start engine.
Specification: approx. battery voltage, fluctuating

NOTE: At certain operating points the engine control module "pulses" the Ground connection for the oxygen sensor heating. In other words, Ground connection constantly cuts in and out at these points. As a result, voltage displayed on measuring instrument may fluctuate.

- Switch off ignition.

If there is no voltage:
- Connect test box V.A.G 1598/31 at wiring harness to engine control module. Actual engine control module is not to be connected. Wiring And Component Check Using Test Box V.A.G 1598/31







- Check for open circuit in the following wiring.

Oxygen sensor upstream of catalytic converter: Bank 1 (Heated Oxygen Sensor -G39-, B1-S1):

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

Oxygen sensor upstream of catalytic converter: Bank 2 (Heated Oxygen Sensor 2 - G108-, B2-S1):

Connector at wiring Test box V.A.G
harness, socket 1598/31, socket
2 4 (Ground)

Oxygen sensor downstream of catalytic converter: Bank 1 (Oxygen Sensor Behind Three Way Catalytic Converter -G130-, B1- S2):

Connector at wiring Test box V.A.G
harness, socket 1598/31, socket
2 63 (Ground)

Oxygen sensor downstream of catalytic converter: Bank 2 (Oxygen Sensor 2 Behind Three Way Catalytic Converter -G131- B2- S2):

Connector at wiring Test box V.A.G
harness, socket 1598/31, socket
2 6 (Ground)

Resistance: max. 1.5 Ohm

If wiring is OK:
- Replace relevant oxygen sensor.