P0131

CIRCUIT DESCRIPTION
The powertrain control module (PCM) supplies a voltage of about 0.45 volt to the oxygen sensor 1 (O2S) 1. The O2S 1 varies the voltage between a range of about 1 volt if the exhaust is rich, down through about 0.10 volt 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-P0204, P0300, P0301-P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set.
^ The 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 8-50 percent.
^ The engine has been in the above conditions for 3.8 seconds.
^ The fuel ethanol composition less than 88 percent.
^ The fuel level more than 10 percent
^ The system voltage more than 10 volts.
^ The engine is operating in Closed Loop.
^ The manifold absolute pressure (MAP) is greater than 25 kPa.

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

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

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 - Computers and Controls Systems. Symptom Related Diagnostic Procedures
^ A cracked O2S-A cracked O2S or poor ground at the sensor can cause a DTC P0131. Refer to Symptoms - Computers and Controls Systems. 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 O2S-A plugged reference port on the O2S will indicate a lower then normal voltage output from the O2S.

Whenever the O2S pigtail wiring, connector or terminal are damaged, replace the entire O2S 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 O2S 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 O2S.

TEST DESCRIPTION

Steps 1-9:

Steps 10-11:

The number below refers to the step number on the diagnostic table.
2. This step determines if the DTC P0131 is the result of a hard malfunction or an intermittent condition. You may need 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 PCM.