P0131

Oxygen Sensor 1 (O2S 1) Circuit:

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 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 "Open Loop" operation.
Conditions For Setting The DTC
- The engine coolant temperature is greater than 70°C (158°F)
- The engine run time is greater than 60 seconds
- The TP angle is between 5% and 50%
- The Air/Fuel ratio is between 14.5 and 14.7
- The engine is operating in "Closed Loop"
- The O2S 1 voltage is less than 295 mV for greater than 113 seconds
- When one or more of the following DTCs are not set, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0300, P0301, P0302, P0303, P0304, P0506, P0507, P1406, P1441.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM 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 three 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.
- DTCs can be cleared by using a scan tool.

Diagnostic Aids
- 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/or loads to confirm.
- Map Sensor - An output that causes the PCM to sense a lower than normal manifold pressure (high vacuum) can cause the system to go lean. Disconnecting the MAP sensor will allow the PCM to substitute a fixed (defaulted) value for the MAP sensor. When the lean condition is gone when the sensor is disconnected, substitute a known good sensor and recheck.
- Fuel contamination - Water, in even small amounts, near the fuel pump inlet be delivered to the fuel injector. The water causes a lean exhaust and a DTC P0131 can set.
- O2S harness - the O2S 1 pigtail may be mis-positioned and contacting the exhaust manifold.
- Engine misfire - A misfire will result in unburned oxygen in the exhaust, which can cause DTC P0131. Go to DTC P0300 and/or Symptoms
- Cracked Oxygen sensor (O2S) - A cracked O2S or poor ground at the sensor can cause a DTC P0131.
- Plugged fuel filter - A plugged fuel filter can cause a lean condition and cause a DTC P0131 to set.
- Plugged Oxygen Sensor (O2S) - A plugged reference port on the Oxygen Sensor (O2S) will indicate a lower then normal voltage output from the O2S.

NOTE: Whenever the oxygen sensor pigtail wiring, connector or terminal are damaged, the entire oxygen sensor assembly must be replaced. 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 and degrade the oxygen sensor's performance.

DTC P0131 - Oxygen Sensor (O2S) Circuit Low Voltage Sensor 1:

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The OBD System Check prompts the Technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
6. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Replacement PCM must be reprogrammed. Refer to the latest Tech line information for programming procedures.