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-.
Special tools and workshop equipment 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 °C.
Test procedure
-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK
Start diagnosis
-- Perform the function test in Diagnostic Mode 06.
If specified values are obtained:
-- Check for possible intermittent connection or rub through of harness.
-- Erase the code. Drive the vehicle and generate the readiness code.
If the specified value was Not obtained:
Checking primary voltage
-- Disconnect the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector -1-.
-- Using a multimeter, connect the negative lead to engine ground. Start the engine, and check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminals 2, 3, 4 and 6 for voltage.
Specified value: 2.40 V - 4.99 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
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 the Repair information.
-- 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 T121 terminals for an open circuit.
| Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminals | Motronic Engine Control Module (ECM) -J220- electrical connector T121 terminals or test box sockets |
|---|---|
| 1 | 52 |
| 2 | 51 |
| 3 | 5 |
| 5 | 71 |
| 6 | 70 |
Specified value: 1.5 Ω 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 Motronic Engine Control Module (ECM) -J220-. Refer to the Repair 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 .