Oxygen Sensor 1 Heater After Catalytic Converter, Checking

Oxygen Sensor 1 Heater after Catalytic Converter, Checking

• Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater ( Z29) is part of Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) ( G130) and cannot be replaced separately.

• When servicing terminals in harness connector of Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) ( G130), use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• Fuse (S344) OK.

• Engine Component Power Supply Relay (J757) OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, shift selector lever into position " P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] General Diagnosis.

Start diagnosis

- Disconnect the electrical harness connector - 2 - from the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) ( G130).





Checking internal resistance

- Using the Multimeter (V.A.G 1526 A) or equivalent, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) electrical harness connector terminals 1 to 2 for resistance.

Specified resistance: 1.0 to 20.0 ohms (at approx. 20° C)





If the specified value is not obtained:

- Replace Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) ( G130). Refer to Fuel Injection and Ignition Repair Information.

If the specified value is obtained:

Checking voltage supply

- Crank the engine (engine may run).

- Using a multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) ( G130) electrical harness connector terminal 1 to Ground (GND) for voltage.









- Switch the ignition off.

Specified value: Battery voltage.

If the specification was not obtained:

- Check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) ( G130) electrical harness connector terminal 1 to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 2/87 an open circuit, a short circuit to each other, Battery (+), or Ground (GND).

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specification was obtained:

Checking Ground (GND) activation

If the manufacturers test box is being used. Perform the following step.

- Install the test box. Refer to Fuel Injection and Ignition Repair Information

If the manufacturers test box is not being used. Perform the following step.

- Remove the Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Service and Repair.

- Using a multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130) electrical harness connector terminal 2 to the Engine Control Module (ECM) (J623) electrical harness connector T94 terminal 7 for resistance.









Specified value: 1.5 ohms max.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

- Replace the Engine Control Module (ECM) (J623 ). Refer to => [ Engine Control Module, Replacing ] Service and Repair.

- Assembly is performed in the reverse of the removal.

Final procedures

After repair work, the following work steps must be performed in the mentioned sequence:

1. Check the DTC memory. => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

End of diagnosis