Oxygen Sensor After Catalytic Converter, Checking Heater

Oxygen Sensor after Catalytic Converter, Checking Heater

• Vehicle must be raised before electrical harness connector for the Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater (Z29) is accessible.

• When servicing terminals in harness connector of Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater (Z29 ), use only gold-plated terminals.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater (Z29) fuse 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 sequence

- Remove the right vehicle floor cover - arrows -.





Checking internal resistance

- Disconnect the Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater (Z29) electrical harness connector - 2 -.





- Using a multimeter, check the Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater ( Z29) electrical harness connector terminals 1 to 2 for resistance.





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

If the specification was not obtained:

- Replace the Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater (Z29). Refer to Fuel Injection and Ignition Repair Information.

If the specification was obtained:

Checking voltage supply

- Using a multimeter, check the Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater ( Z29) electrical harness connector terminal 1 to Fuel Pump Relay (J17) terminal 2 for an open circuit.





- Turn key on:

Specified value: 12.5Battery voltage.

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, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

- Turn key off.

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 Motronic Engine Control Module (ECM) ( J220). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Using a multimeter, check the Oxygen Sensor (O2S) 1 (behind Three Way Catalytic Converter (TWC)) Heater ( Z29) electrical harness connector terminal 2 to the Motronic Engine Control Module (ECM) (J220) electrical harness connector terminal 63 for an open circuit according to the wiring diagram.









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, lose 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:

- Replace the Motronic Engine Control Module (ECM) (J220). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Install the right vehicle floor cover.

Final procedures

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

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

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

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End of diagnosis.