P0131
DTC P0131 O2S Circuit Low Voltage Sensor 1
Circuit Description
The Powertrain Control Module (PCM) supplies a voltage of about 0.45 volts to oxygen sensor 1 (O2S 1).
The O2S 1 voltage varies from about 1 volt if the exhaust is rich, to about 0.10 volt if the exhaust is lean.
The O2S 1 circuit is open and produces no voltage when the O2S 1 temperature is below 315° C (600° F). An open O2S 1 circuit or a cold sensor causes an open loop operation.
Conditions for Running the DTC
- There are no active MAP DTCs
- There are no active IAT DTCs
- There are no active ECT DTCs
- There are no active TP DTCs
- There are no active Fuel Trim DTCs
- There are no active Injector Control DTCs
- There are no active Misfire DTCs
- There are no active CKP DTCs
- There are no active EVAP DTCs
- There are no active IAC DTCs
- There are no active PCM Memory DTCs
- The air flow is more than 3 grams per second.
- The engine coolant temperature (ECT) is more than 70° C (158° F).
- The engine is operating in Closed Loop.
- The throttle position (TP) angle is between 5 percent and 50 percent.
- The engine has been in the above condition for 20 seconds.
Conditions for Setting the DTC
The O2S 1 voltage is less than 44 mV for 125 seconds.
Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive ignition cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is recorded in the scan tool's Freeze Frame and Failure Records.
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.
- The DTCs can be cleared using the scan tool Clear Information function.
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 speeds and loads in order to confirm the diagnosis. Refer to Fuel System Diagnosis.
- The map sensor - A MAP output that indicates a lower than normal manifold pressure, or high vacuum, can cause the system to go lean. Disconnecting the MAP sensor will cause the PCM to substitute a default value for the MAP output. If the lean condition disappears when the MAP sensor is disconnected, substitute a known good sensor and check the system again.
- Fuel contamination - Even small amounts of water near the fuel pump inlet can be delivered to the fuel injector. Water causes a lean exhaust, which may cause DTC P0131 to set.
- The O2S harness - The O2S 1 pigtail may be positioned incorrectly. Ensure that the pigtail is not contacting the exhaust manifold.
- An engine misfire - A misfire will result in unburned oxygen in the exhaust stream, which can cause DTC P0131.Go to DTC P0300 Engine Misfire Detected and the Driveability Symptoms.
- A cracked oxygen sensor (O2S) - A cracked O2S or a poor ground at the sensor can cause a DTC P0131. Go to the Symptoms.
- 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 produce a lower than normal voltage output from the O2S.
Steps 1 - 4:
Steps 5 - 8:
Steps 9 - 11:
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 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 PCM.
9. Program the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline information for PCM programming.