P0131

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) supplies a voltage of about 0.45 volts to the Oxygen Sensor 1 (O2S 1). The O2S 1 varies the voltage between a range of about 1.0 volts if the exhaust is rich, down through about 0.10 volts if the exhaust is lean.

The O2S 1 is like an open circuit and produces no voltage when the O2S 1 temperature is below 315°C (600°F). An open O2S 1 circuit or cold sensor causes an Open Loop operation.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0169, P0171, P0172, P0178, P0179, P0201, P0202, P0203, P0204, P0300, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set.
^ Engine run time is more than 10 seconds.
^ The Engine Coolant Temperature (ECT) is more than 70°C (158°F).
^ The Throttle Position (TP) angle is between 8 percent and 50 percent.
^ Engine has been in the above conditions for 3.8 seconds.
^ Fuel ethanol composition less than 88 percent.
^ Fuel level more than 10 percent
^ System voltage more than 11.7 volts.
^ Engine is operating in Closed Loop.

CONDITIONS FOR SETTING THE DTC
O2S 1 voltage is less than 52 mV for 125 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The Malfunction Indicator Lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the malfunction active.
^ The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
^ A history DTC stores.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
^ A history DTC will clear after 40 consecutive warm up cycles without a fault.
^ A scan tool can clear the DTCs.

DIAGNOSTIC AIDS
^ The fuel pressure-System will run lean if the fuel pressure is too low. Monitor the fuel pressure while driving the vehicle at various road speeds and loads in order to confirm. Refer to Fuel System Diagnosis. Component Tests and General Diagnostics
^ The MAP sensor-An output that causes the PCM to sense a lower than normal manifold pressure, or high vacuum, can cause the system to go lean. Disconnecting the MAP sensor will allow the PCM to substitute a fixed or defaulted value for the MAP sensor. When the lean condition is gone when the sensor is disconnected, substitute a known good sensor and recheck.
^ A fuel contamination-Water, in even small amounts near the fuel pump inlet, can be delivered to the fuel injector. The water causes a lean exhaust and a DTC P0131 can set.
^ The O2S harness-The O2S 1 pigtail may be mis-positioned and contacting the exhaust manifold.
^ An engine misfire-A misfire will result in unburned oxygen in the exhaust, which can cause DTC P0131. Refer to Symptoms. Symptom Related Diagnostic Procedures
^ A cracked oxygen sensor (O2S)-A cracked O2S or poor ground at the sensor can cause a DTC P0131. Refer to Symptoms. Symptom Related Diagnostic Procedures
^ A plugged fuel filter- A plugged fuel filter can cause a lean condition and cause a DTC P0131 to set.
^ A plugged oxygen sensor (O2S)-A plugged reference port on the oxygen sensor (O2S) will indicate a lower then normal voltage output from the O2S.

Whenever the oxygen sensor pigtail wiring, connector or terminal are damaged, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, the O2S must have a clean air reference provided. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the O2S sensor wires, connectors, or terminals could result in the obstruction of the air reference degrading the performance of the oxygen sensor.

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data that is captured when the malfunction occurred. The scan tool stores this data for later reference.
2. This step determines if the DTC P0131 is the result of a hard malfunction or an intermittent condition. It may be necessary to operate the vehicle within the Freeze Frame conditions and Conditions for Setting the DTC in order to duplicate the malfunction that was detected by the Powertrain Control Module (PCM).
9. Program the replacement PCM and perform the Crankshaft Position System Variation Learn Procedure. Refer to the latest Techline(TM) information for PCM programming.