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 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
| • | No active MAP DTCs |
| • | No active IAT DTCs |
| • | No active ECT DTCs |
| • | No active TP DTCs |
| • | No active fuel trim DTCs |
| • | No active injector control DTCs |
| • | No active misfire DTCs |
| • | No active CKP DTCs |
| • | No active EVAP DTCs |
| • | No active IAC DTCs |
| • | No active PCM memory DTCs |
| • | Air flow is more than 3 grams per second |
| • | Engine coolant temperature (ECT) is more than 70°C (158°F) |
| • | Engine is operating in closed loop |
| • | Throttle position (TP) angle is between 5 percent and 50 percent |
| • | Engine has been in the above conditions for 3.8 seconds |
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) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tools Freeze Frame and Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
| • | The fuel pressure -- If the fuel pressure is too low, the system will run lean . Monitor the fuel pressure while driving the vehicle at various road speeds and loads in order to confirm the proper fuel pressure. Refer to Fuel System Diagnosis . |
| • | 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. |
| • | 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 . |
| • | A cracked oxygen sensor (O2S) -- A cracked O2S or poor ground at the sensor can cause a DTC P0131. Refer to 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 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 may result in the obstruction of the air reference degrading the performance of the oxygen sensor.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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This DTC failing during power enrichment operation (TP angle above 60 percent) may indicate a condition described in Diagnostic Aids. If this DTC test passes while the Fail Records conditions are being duplicated, an intermittent condition is indicated. Review the Fail Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.
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The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be performed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Does the O2 sensor voltage remain below the specified value? | 52 mV | Go to Diagnostic Aids | |
Does the O2 sensor voltage read within the specified values? | 351 mV - 551 mV | |||
4 |
Did you find and correct the condition? | -- | ||
5 | Replace the O2 Sensor. Refer to Oxygen Sensor Replacement . Did you complete the replacement? | -- | -- | |
|
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming Did you complete the replacement? | -- | -- | ||
7 |
Does the DTC reset? | -- | System OK |
