Heated Oxygen Sensor, Checking

Heated Oxygen Sensor, Checking

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Engine Component Power Supply Relay (J757) OK.

• Fuse (SB9) OK.

• Battery voltage at least 12.5 volts.

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

• 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 => [ Preliminary Check ] Preliminary Check.

Function test

- Perform the function test in Diagnostic Mode 06 => [ Diagnostic Mode 06 - Read Test Results for Specific Diagnostic Functions ] Diagnostic Mode 06 - Read Test Results for Specific Diagnostic Functions.

If the specified values are not obtained:

Start diagnosis

- Remove the engine cover with air filter.

If the specified values are not obtained:

Checking primary voltage

- Disconnect the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - arrow -.





- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) terminals 1 to 5 for voltage.





- Crank the engine.

Specified value: 0.4 to 0.5 V

- Switch the ignition off.

If the specified value is obtained:

- Replace the Heated Oxygen Sensor (HO2S) (G39).

If the specified value was not obtained:

Checking wiring

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

- Install the test box.

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 ] Engine Control Module.

- Using a Multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminals to the Motronic Engine Control Module (ECM) (J220) electrical harness connector T94 terminals for an open circuit.









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 found in the wiring:

- 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 not OK:

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

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

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 ] Monitors, Trips, Drive Cycles and Readiness Codes.