Oxygen Sensor O2S Heater, Checking
Oxygen Sensor O2S Heater, Checking
Observe all safety precautions: => [ Safety Precautions ] Generic Scan Tool
View clean working conditions: => [ Clean Working Conditions ] Clean Working Conditions
Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.
For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.
Oxygen Sensor (O2S) Heater (Z19) is part of Heated Oxygen Sensor (HO2S) (G39) and cannot be replaced separately.
Special tools, testers and auxiliary items required
• multimeter.
• Wiring diagram.
Test requirements
• Fuse (SB6) OK.
• Motronic Engine Control Module (ECM) Power Supply Relay (J271) 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 (GND) 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 engine cover with air filter. Refer to the appropriate service manual.
Checking internal resistance
- Disconnect the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector - 1 -.
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) terminals 3 to 4 for resistance.
Specified value: 2.5 to 10.0 ohms (at approx. 20° C)
If the specification was not obtained:
- Replace the Heated Oxygen Sensor (HO2S) (G39). Refer to the appropriate service manual.
If the specification was obtained:
Checking voltage supply
- Crank the engine (engine may run).
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 4 to Ground (GND) for voltage.
- Switch the ignition off.
Specified value: Battery voltage.
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 an open circuit, a short circuit to each other, Battery (+), or Ground (GND).
- 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 (GND) activation
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 appropriate service manual.
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) (G39) electrical harness connector terminal 3 to the Engine Control Module (ECM) (J623) electrical harness connector T94 terminal 51 for resistance.
Specified value: 1.5 ohms max.
If the specification was not obtained:
- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
- 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 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 ] Readiness Code.
If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:
- Replace the Engine Control Module (ECM) (J623). Refer to the appropriate service manual.
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 ] Readiness Code