P0139
DTC P0139: HO2S Slow Response Sensor 2Wiring Diagram:
Circuit Description
The Engine Control Module (ECM) supplies a voltage of about 0.45 V between the ECM terminals C62 and C4. The Heated Oxygen (HO2) sensor varies the voltage within a range of about 1 V if the exhaust is rich, down to about 0.1 V if the exhaust is lean. The HO2 sensor is like an open circuit and produces no voltage when it is below 360 °C (600 °F). An open HO2 sensor circuit or a cold HO2 sensor causes "Open Loop" operation.
Action Taken When the DTC Sets
- Response time for stage 1 ICMD Fuel Shift or stage 2 is greater than 25 seconds.
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after four consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- The DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Normal scan tool voltage varies between 0.15 - 8.5 mV while in Closed Loop. If DTC P0139 is intermittent, refer to Intermittents Intermittents
Step 1-13:
Troubleshooting