Oxygen Sensor Bank 1 Sensor 1 Heater Checking
Oxygen Sensor Bank 1 Sensor 1 Heater Checking
• Oxygen Sensor (O2S) Heater (Z19) is part of Heated Oxygen Sensor (HO2S) (G39) and cannot be serviced separately.
• When servicing terminals in the electrical harness connector of Heated Oxygen Sensor (HO2S) (G39), use only gold-plated terminals.
Special tools, testers and auxiliary items required
• Multimeter.
• Wiring diagram.
Test requirements
• Fuse (SB11) OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, shift selector lever into position "P" or "N".
• A/C switched off.
• Ground 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.
Start diagnosis
- Remove the air filter.
- Disconnect the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - 2 -.
Checking internal resistance
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) terminals 3 to 4 for resistance.
Specified value: 1.5 to 10.0 ohms (at approx. 20° C)
If the specification was Not obtained:
- Replace the Heated Oxygen Sensor (HO2S) (G39).
If the specification was obtained:
Checking voltage supply
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 4 to ground for voltage.
- Crank the engine.
Specified value: Battery voltage.
- Switch the engine Off.
If the specification was Not obtained:
- Check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 4 to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 2/87 for an open circuit, a 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 the specification was obtained:
Checking Ground activation
If the specified value was Not obtained:
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 Engine Control Module (ECM) (J623). Refer to the Repair Information.
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector to the Engine Control Module (ECM) (J623) electrical harness connector T121 for resistance.
Specified value: 1.5 ohms max.
If the specification was Not obtained:
- Check the wiring for an open circuit, high resistance, a 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 if the voltage supply was OK:
- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
- Perform a road test to verify repair.
If the DTC does Not return:
Generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If the DTC returns, no malfunction is found in the wiring and the voltage supply was OK:
- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.
- Assembly is performed in the reverse of the removal.
Final procedures
After 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.