Oxygen Sensor (O2S) 2 Heater Z28, Checking

Oxygen Sensor (O2S) 2 Heater Z28, Checking

NOTE:
- Oxygen Sensor (O2S) 2 Heater Z28 is part of Heated Oxygen Sensor (HO2S) 2 G108 and cannot be serviced separately.
- When servicing terminals in the electrical harness connector of Heated Oxygen Sensor (HO2S) 2 G108, use only goldplated terminals.

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram.

Test requirements
- Fuse SB33 fuse 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.

NOTE: The voltage for the Oxygen Sensor (O2S) 2 Heater Z28 is supplied by the Motronic Engine Control Module (ECM) Power Supply Relay 2 J670.

Test procedure
- Perform a preliminary check to verify the customers complaint. Preliminary Check

Start diagnosis







- Disconnect the Heated Oxygen Sensor (HO2S) 2 G108 electrical harness connector - 4 -.

Checking internal resistance
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 2 G108 terminals 3 to 4 for resistance.

Specified value: 2.5 to 10.0 Ohms (at approx. 20 degrees C)

If the specification was not obtained:
- Replace Heated Oxygen Sensor (HO2S) 2 G108.

If the specification was obtained:

Checking voltage supply
Switch the ignition on.







- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 2 G108 electrical harness connector terminal 3 to Ground (GND) for voltage.

Heated Oxygen Sensor (HO2S) Measure to
2 G108 electrical
harness connector terminal
3 Ground (GND)

Specified value: Battery voltage.
Switch the ignition off.

If the specification was not obtained:
- Check the Heated Oxygen Sensor (HO2S) 2 G108 electrical harness connector terminal 3 to the Motronic Engine Control Module (ECM) Power Supply Relay 2 J670 terminal 2/87 for a short circuit to each other, Ground (GND), or an open circuit.
- 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 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.
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) electrical harness connector to the Engine Control Module (ECM) J623 electrical harness connector T94 for an open circuit.

Heated Oxygen Sensor (HO2S) Engine Control Module (ECM)
2 G108 electrical harness J623 electrical connector T94
connector terminal terminal or test box socket
4 73

Specified value: 1.5 Ohms max.

If the specification was not obtained:
- Check the wiring for a short circuit to each other, Battery (+), Ground (GND) or an Open circuit.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
- Erase the DTC memory. Diagnostic Modes 01 - 09.
- Perform a road test to verify repair.

If the DTC does not return:
Repair complete, Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:
- Replace the Motronic Engine Control Module (ECM) J623.
- Assembly is performed in the reverse of the removal.

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:

1. Check the DTC memory. Diagnostic Modes 01 - 09
2. If necessary, erase the DTC memory. Diagnostic Modes 01 - 09
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

End of Diagnosis