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 And Workshop Equipment Required
- Multimeter.
- Wiring diagram.
Test Requirements
- The Heated Oxygen Sensor (HO2S) -G39- fuse OK.
- The Oxygen Sensor (O2S) Heater -G39- 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 °C.
Test Procedure
-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK
If an O2 sensor heater code is also set, perform the test for the O2 heater first.
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 "Test-ID 01: Oxygen sensor monitoring before catalytic converter".
-- Select "Test-ID 131: Dynamic test".
-- Check the specified values at idle.
| Dynamic test | Specified value | ||
|---|---|---|---|
| min. | max. | ||
| Normal operation | 0.350 | - | |
| Reduced threshold upon suspicion of malfunction in catalytic converter | 0.399 | - | |
If the specified value was obtained:
-- Switch the ignition OFF. Fault is not active at this time. Check for poor connections, loose terminals and harness check.
If the specified value was Not obtained:
Checking primary voltage
-- Disconnect the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector -1-.
-- Using a multimeter, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector -1- terminals 1 to 2 for voltage.
Specified value: 0.400 to 0.500 Volts
If the specified value was obtained:
-- Replace the Heated Oxygen Sensor (HO2S) -G39- Refer to the appropriate Service Information.
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) -J623-. Refer to the appropriate Service 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.
| Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminals | Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminals or test box sockets |
|---|---|
| 1 | 78 |
| 2 | 79 |
| 5 | 56 |
| 6 | 57 |
Specified value: 1.5 Ω 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 found in the wiring:
-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate Service Information.
Final Procedures
After the repair work, the following work steps must be performed in the following sequence:
- Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
- If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
- If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .