Oxygen Sensor O2S Heater, Checking
Observe all safety precautions: SAFETY PRECAUTIONS
View 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 and workshop equipment required
- multimeter.
- Wiring diagram.
Test requirements
- Fuse -S14- 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 .
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 Ω (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.
| Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal | Engine Control Module (ECM) -J623- electrical harness connector T94 terminal or test box socket |
|---|---|
| 4 | Ground (GND) |
-- 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- terminal 8 for 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 73 for resistance.
| Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal | Engine Control Module (ECM) -J623- electrical harness connector T94 terminal or test box socket |
|---|---|
| 3 | 51 |
Specified value: 1.5 Ω 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 .
-- Perform a road test to verify repair.
If the DTC does not return:
Generate readiness code. Refer to 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:
- 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