P0131

DTC P0131: HO2S Circuit Low Voltage Bank 1 Sensor 1

Wiring Diagram:

Circuit Description
The Engine Control Module (ECM) supplies a voltage of about 0.45 V between the ECM terminals K11 and K12. The Oxygen (O2) 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 O2 sensor is like an open circuit and produces no voltage when it is below 300 degrees C (600 degrees F). An open O2 sensor circuit or a cold O2 sensor causes "Open Loop" operation.

Conditions for Setting the DTC
- Ignition ON.
- No CKP fault exists.
- Oxygen sensor is ready.
- Mass air flow is 12 kg/h or greater.
- HO2S voltage is less than 0.2 V, and internal resistance of the HO2S is less than 30 Ohms.

Action Taken When the DTC Sets
- 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 at the end of 3 consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
Normal scan tool voltage varies between 0.1 and 1.0 V while in Closed Loop. Inspect the Oxygen (O2) sensor wire. The O2 sensor may be positioned incorrectly and contacting the exhaust manifold. Check for an intermittent ground in the wire between the O2 sensor and the engine control module. Perform an injector balance test to determine if a restricted fuel injector may be causing the lean condition. Vacuum of crankcase leaks will cause a lean running condition. An exhaust manifold gasket leak of a cracked exhaust manifold may cause outside air to be pulled into the exhaust and past the sensor.

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DTC Troubleshooting