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Home >> Jeep >> 2007 >> Liberty Limited, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> DTCS P0112 To P0155 - Gas >> P0138-O2 Sensor 1/2 Circuit High >> Diagnostic Test
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Diagnostic Test

  1. 1) ACTIVE DTC 
    NOTE: If an O2 sensor signal circuit is shorted to voltage, all O2 sensor voltage readings displayed on the scan tool will be approximately 5.0 volts. Diagnose the sensor that set the most current DTC.

    Start the engine and allow it to idle for at least 60 seconds.

    WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

    With a scan tool, select View DTCs.

    Is the DTC Active at this time? 

    Yes 

    1. Go to  2).

    No 

    1. Refer to INTERMITTENT CONDITION Diagnostic Procedure.
  2. 2) (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO VOLTAGE 
    Fig 1: Checking O2 Sensor Signal Circuit Voltage
    GC0038464Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Disconnect the C1 and C2 PCM harness connectors.

    Disconnect the 1/2 O2 Sensor harness connector.

    Turn the ignition on.

    Measure the voltage on the (K141) O2 Sensor 1/2 Signal circuit in the O2 Sensor harness connector.

    NOTE: Measure the voltage in reference to ground, not the (K904) O2 Return Downstream circuit.

    Is there any voltage present? 

    Yes 

    1. Repair the short to voltage in the (K141) O2 Sensor 1/2 Signal circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  3).
  3. 3) (K904) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO VOLTAGE 
    Fig 2: Checking Voltage In O2 Sensor Return Upstream & Downstream Circuits
    GC0038465Courtesy of CHRYSLER LLC

    Measure the voltage on the (K904) O2 Return Downstream circuit in the O2 Sensor harness connector.

    Is there any voltage present? 

    Yes 

    1. Repair the short to voltage in the (K904) O2 Return Downstream circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  4).
  4. 4) O2 SENSOR 
    Fig 3: Checking O2 Sensor Return Upstream & Downstream Circuits
    GC0038466Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Connect the C1 and C2 PCM harness connectors.

    Ignition on, engine not running.

    With a scan tool, monitor the 1/2 O2 Sensor voltage.

    Connect a jumper wire between the (K141) O2 1/2 Signal circuit and the (K904) O2 Return Downstream circuit in the 1/2 O2 Sensor harness connector.

    Is the voltage between 2.3 and 2.7 volts with the jumper wire installed? 

    Yes 

    1. Replace the O2 Sensor.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go to  5).
      NOTE: Remove the jumper wire before continuing.
  5. 5) (K141) O2 1/2 SIGNAL CIRCUIT OPEN 
    Fig 4: Checking O2 1/2 Sensor Signal Circuit For Open
    GC0038470Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Disconnect the C1 and C2 PCM harness connectors.

    CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

    Measure the resistance of the (K141) O2 1/2 Signal circuit from the O2 Sensor harness connector to the appropriate terminal of special tool #8815.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Go to  6).

    No 

    1. Repair the open in the (K141) O2 1/2 Signal circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .
  6. 6) (K904) O2 RETURN DOWNSTREAM CIRCUIT OPEN 
    Fig 5: Checking O2 Return Circuit For Open
    GC0038471Courtesy of CHRYSLER LLC

    Measure the resistance of the (K904) O2 Return Downstream circuit from the O2 Sensor harness connector to the appropriate terminal of special tool #8815.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Go to  7).

    No 

    1. Repair the open in the (K904) O2 Return Downstream circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .
  7. 7) PCM 
    NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

    Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

    Were there any problems found? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Replace and program the Powertrain Control Module per Service Information.
    2. Perform POWERTRAIN VERIFICATION TEST .