Oxygen Sensor Before Catalytic Converter, Checking

Oxygen Sensor before Catalytic Converter, Checking

• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the Heated Oxygen Sensor (HO2S) (G39/Z19).

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Heated Oxygen Sensor (HO2S) (G39) fuse OK.

• The Oxygen Sensor (O2S) Heater (Z19) before catalytic converter OK. (No heater code set).

• Battery voltage at least 12.5 volts.

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

• A/C switched off.

• Ground connections between engine/transmission/chassis OK.

• Exhaust system between catalytic converter and cylinder head properly sealed.

• Coolant Temperature at least 80 °C.

Test procedure

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

Start diagnosis

- Connect scan tool.

- Start the engine and let it run at idle.

- Select "Diagnostic mode 6: Check test results of components that are not continuously monitored".

- Select "Monitor-ID $01: Oxygen sensor monitoring before catalytic converter".

- Select "Test-ID $83: Dynamic test".

- Check the specified values at idle.






If the specified value was obtained:

- Switch the ignition OFF. Generate the readiness code.

If the specified value was Not obtained:

Checking primary voltage

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

- Using a multimeter, connect the negative lead to engine ground. Check each of the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminals 1,2,5, and 6 for voltage.

Specified value: 2.40 V - 3.10 V

- Switch the ignition OFF.

If the specified value was obtained:

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

If the specified value was Not obtained:

Checking wiring

- Remove the Engine Control Module (ECM) (J623). Refer to the Repair Information.

- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminals to the Engine Control Module (ECM) (J623) electrical harness connector T94 terminals for an open circuit. Refer to Wiring Diagrams for pin locations.






Specified value: 1.5 ohms Max.

If the specified value was Not obtained:

- Check the wiring for an open, high resistance, short circuit to each other, Battery (+) or Ground.

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

- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring and the voltage was Not OK:

- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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