Circuit Description
The Powertrain Control Module (PCM) supplies a voltage of approximately 0.45 volt between the oxygen sensor (O2S 1) signal and the ground circuit. The oxygen sensor (O2S 1) varies the voltage within a range of approximately 1 volt if the exhaust is rich, to approximately 0.10 volt if the exhaust is lean.
The sensor is like an open circuit and produces no voltage when below 315°C (600°F). An open sensor circuit or a cold sensor causes an Open Loop operation.
Replace the entire oxygen sensor (O2S 1) assembly. Do not attempt to repair the oxygen sensor if the following conditions exist:
| • | Damaged wiring |
| • | Damaged electrical connectors |
| • | Damaged terminals |
Conditions For Setting The DTC
| • | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0171, P0200, P0300, P0301, P0302, P0303, P0304, P0341, P0404, P0506, P0507, P0601, P0602 not set. |
| • | Air flow is greater than 3 grams per second. |
| • | Engine Coolant Temperature (ECT) is greater than 70°C (158°F). |
| • | Engine is operating in Closed Loop. |
| • | Throttle Position (TP) angle is between 8% and 50%. |
| • | Engine has been in the above conditions for 20 seconds. |
| • | O2S 1 voltage is less than 52 mV for 125 seconds. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will illuminate. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns ON. |
| • | The vehicle will operate in an Open Loop operation. |
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. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
| • | Fuel pressure--The system will be lean if the pressure is too low. It may be necessary to monitor the fuel pressure while driving the vehicle at various road speeds and/or loads in order to confirm. Refer to Fuel System Diagnosis . |
| • | 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 (default) value for the MAP sensor. If the lean condition is no longer present when you disconnect the sensor, substitute a known good sensor and recheck the condition. Refer to Manifold Absolute Pressure Sensor Output Diagnosis . |
| • | Fuel contamination--Water, even in small amounts, near the in-tank fuel pump inlet, can travel to the fuel injector. The water causes a lean exhaust and can set DTC P0131. |
| • | Sensor harness--Ensure that the O2S 1 sensor pigtail is not contacting the exhaust manifold. |
| • | Engine misfire--A misfiring cylinder will result in unburned oxygen in the exhaust, which could cause DTC P0131. Go to DTC P0300 Engine Misfire Detected and/or Symptoms. |
| • | Cracked Oxygen sensor (O2S 1)--A cracked O2S 1 or poor ground at the sensor could cause a DTC P0131. Go to Symptoms. |
| • | Plugged fuel filter--A plugged fuel filter can cause a lean condition and cause a DTC P0131 to set. |
| • | Plugged Oxygen Sensor (O2S 1)--A plugged reference port on the Oxygen Sensor (O2S 1) will indicate a lower then normal voltage output from the O2S 1. |
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
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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.
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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.
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This step simulates a DTC P0134. If the PCM senses the change, the PCM and wiring are OK.
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Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline information for PCM programming and the Crankshaft Position System Variation Learn for the Crankshaft Position System Variation Learn Procedure.
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If no malfunctions have been found at this point and if no additional DTCs were set, refer to the Diagnostic Aids for additional checks and information.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Does the O2S 1 voltage remain below the specified value? | 52 mV | |||
3 |
Does the O2S 1 voltage stay below specified value? | 52 mV | ||
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Does the scan tool indicate that the O2S 1 voltage is within the specified values? | 399-499 mV | Go to Diagnostic Aids | ||
5 |
Was a repair necessary? | -- | ||
Is the action complete? | -- | -- | ||
7 |
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
