P0139

P0139
Aging of Oxygen Sensor After Three Way Catalytic Converter (TWC) (cylinders 1-3)

Function
To diagnose the oxygen sensor signals, the Engine Control Module (ECM) uses the form and frequency of the respective signal as a measuring value. The data to be calculated by the ECM are the time of the sensor voltage between positive and negative limits, the maximum and the minimum recognized sensor voltage values, oxygen sensor value toward rich, oxygen sensor value toward lean, sensing limits of oxygen sensing toward rich, sensing range of oxygen sensing, period duration of sensors ahead of the Three Way Catalytic Converter (TWC) and the sensor voltage ahead of the TWC.

Diagnosis Conditions
Diagnostic Trouble Code (DTC) P0139 is stored in the Engine Control Module (ECM), when the sensor voltage is without interruptions longer than 9 sec. between 0.0623 V to 0.0399 V, i.e. the sensors deliver a signal which is implausible for the ECM.

Conditions for the diagnosis of oxygen sensor signals:
- Sensor heating is active.
- Oxygen sensing is active.
- Sensor voltage ahead and after TWC is active.
- No Secondary Air Injection.
- No faults detected for fuel tank ventilation and Secondary Air Injection.

NOTE: If DTC P0139 is stored, heat oxygen sensors by road testing under load, running engine at high rpm with no load. Erase DTC memory and road test again during which the engine rpm must be between 950 1/min and 3000 1/min for 120 sec. Now read DTC memory again. If DTC P0139 is found again, replace the respective oxygen sensor.





Diagnosis procedure
Connect system tester or scan tool and advance to menu point "DTC memory".
1. Connect system tester or scan tool with adapter cable.
2. Switch ignition on.
3. Initiate diagnosis and advance to menu point "DTC memory"
4. Read DTC memory.

- If other DTCs are in memory: Read DTC memory and correct faults.
- If DTC P0139 is in memory: Road test after DTC memory is erased.

Read DTC memory, correct faults
1. Read DTC memory.
2. Correct fault according to Repair Manual.
3. Erase DTC memory.
4. Afterwards road test vehicle as described in "NOTE" above.
5. Read DTC memory again.

- If no fault found: End
- If DTC P0139 found: Continue

Road test after DTC memory was erased
1. Erase DTC memory.
2. Heat oxygen sensors (road test vehicle under load, run engine under no load at high engine speed).
3. Road test vehicle. Engine speed must be between 950 1/min and 3000 1/min for 120 sec. while engine is at operating temperature.
4. Connect system tester or scan tool and advance to menu point "DTC memory".

- If no fault found: End
- If DTC P0139 is stored: Replace oxygen sensor.