Oxygen Sensor Regulation Before Catalytic Converter, Checking
Oxygen Sensor Regulation Before Catalytic Converter, Checking
• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the Heated Oxygen Sensor (HO2S) (G39).
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.
• 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 80.3 °C.
• Ignition switched OFF.
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 $131: Dynamic test".
- Check the specified values at idle.
If the specified values were obtained:
- Switch the ignition OFF. Fault is not active at this time. Check for poor connections, loose terminals and perform a harness check.
If the specified values are Not obtained:
Checking primary voltage
- Disconnect the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - 1 -.
- Turn the ignition ON.
- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminals 1 and 5 for voltage.
Specified value: 2.45 to 2.99 Volts
If the specified value was obtained:
- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 2 for voltage
Specified value: 2.25 to 2.79 Volts
If the specified value was obtained:
- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 6 for voltage
- Turn the ignition switch OFF.
Specified value: 3.25 to 3.79 Volts
If the specified value was obtained:
- Replace the Heated Oxygen Sensor (HO2S) (G39). Refer to the repair information.
If any of the above specified values were 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) (J623). Refer to the repair information.
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminals to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T94 terminals for an open circuit.
Specified value: 1.5 ohms Max.
If the specified value was Not obtained:
- Check the wiring for an open, high resistance or short to ground.
- 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 Not OK:
- Replace the Motronic 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.