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 the temperature is less than 315°C (600°F). An open sensor circuit or a cold sensor causes an open loop operation.
Replace the entire 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 Running The DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set. |
| • | The air flow is more than 3 grams per second (g/sec). |
| • | 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 conditions for 20 seconds. |
Conditions For Setting The DTC
O2S 1 voltage is less than 52 mV for 125 seconds.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | 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. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
| • | Fuel pressure -- The system will be lean if the fuel pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads in order to confirm this condition. Refer to the Fuel System Diagnosis . |
| • | The MAP sensor -- An output that causes the PCM to sense a lower than normal manifold pressure, or a high vacuum, can cause the system to go lean. Disconnecting the MAP sensor will allow the PCM to substitute a fixed, or a default, value for the MAP sensor. If the lean condition is gone when the MAP sensor is disconnected, refer to Manifold Absolute Pressure Sensor Output Diagnosis for further diagnosis. |
| • | Fuel contamination -- Even small amounts or water near the in-tank fuel pump inlet can be delivered to the injector. The water causes a lean exhaust and can set a DTC P0131. |
| • | The sensor harness -- The O2S 1 sensor pigtail may be mis-positioned and contacting the exhaust manifold. |
| • | An engine misfire -- A misfiring cylinder will result in unburned oxygen in the exhaust, which could cause a DTC P0131. Refer to DTC P0300 Engine Misfire Detected or Symptoms . |
| • | A cracked oxygen sensor (O2S 1) -- A cracked O2S 1 sensor or a faulty ground at the O2S 1 sensor could 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 1) -- A plugged reference port on the Oxygen Sensor (O2S 1) will indicate a lower then normal voltage output from the O2S 1 sensor. |
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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The Powertrain OBD System Check prompts you to complete some of the basic diagnostics and to store the Freeze Frame and Failure Records data on the scan tool, if applicable. This creates an electronic copy of the data that was 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 powertrain control module (PCM).
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Program the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline™ information for PCM programming.
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||||||
Is the O2S voltage fixed less than the value specified? | 44 mV | |||||||||||||
3 | This DTC is intermittent. Are any additional DTCs stored? | -- | Go to Diagnostic Aids | |||||||||||
4 |
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 voltage is within the specified values? | 351 - 551 mV | ||||||||||||
5 | The O2S may be detecting a lean exhaust condition. Check for one of the following conditions:
Repair any of the above or similar engine conditions as necessary. Did you find a problem? | -- | ||||||||||||
6 |
Is the resistance at the specified value? | ∞ | ||||||||||||
7 | Repair the O2S signal HIGH circuit that has shorted to ground. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||
8 | Replace the O2S. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |||||||||||
|
Important:: Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | ||||||||||||
10 |
Does the scan tool indicate the diagnostic Passed? | -- | ||||||||||||
11 | Does the scan tool display any additional undiagnosed DTCs? | -- | System OK |
