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Home >> Jeep >> 2005 >> Grand Cherokee Limited, 5.7 2 >> Repair and Diagnosis >> Engine Performance >> System >> DTCS P0121 To P0171 >> Diagnosis And Testing >> P0139-O2 Sensor 1/2 Slow Response >> Diagnostic Test

Diagnostic Test

  1. 1)  ACTIVE DTC 
    NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.

    Ignition on, engine not running.

    NOTE: After the repairs have been made, verify proper O2 Sensor operation. If all the O2 Sensor voltage readings have not returned to normal, follow the diagnostic procedure for the remaining O2 Sensors.

    With a scan tool, read DTCs.

    Is the DTC active at this time? 

    Yes 

    1. Go To step  2).

    No 

    1. Refer to INTERMITTENT CONDITION .
    2. Perform POWERTRAIN VERIFICATION TEST .
  2. 2)  EXHAUST LEAK 

    Start the engine.

    Inspect the exhaust system for leaks between the engine and the O2 Sensors.

    Are there any exhaust leaks? 

    Yes 

    1. Repair or replace the leaking exhaust parts as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  3).
  3. 3)  (K141) O2 1/2 SIGNAL CIRCUIT 
    Fig 1: Checking O2 Sensor Signal Circuit
    GC0027073Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off

    Disconnect the 1/2 O2 Sensor harness connector.

    Ignition on, engine not running.

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

    Is the voltage between 4.5 and 5.0 volts? 

    Yes 

    1. Go To step  4).

    No 

    1. Check the (K141) O2 1/2 Signal circuit for a short to ground, open, or short to voltage. If OK, replace and program the Powertrain Control Module per Service Information.
    2. Perform POWERTRAIN VERIFICATION TEST .
  4. 4)  (K904) O2 RETURN DOWNSTREAM CIRCUIT 
    Fig 2: Checking O2 Sensor Return Circuit
    GC0027071Courtesy of DAIMLERCHRYSLER CORP.

    Measure the voltage on the (K904) O2 Return Downstream circuit in the 1/2 O2 Sensor harness connector.

    Is the voltage at 2.5 volts? 

    Yes 

    1. Go To step  5).

    No 

    1. Check the (K904) O2 Return Downstream circuit for a short to ground, open, or short to voltage. If OK, replace and program the Powertrain Control Module per Service Information.
    2. Perform POWERTRAIN VERIFICATION TEST .
  5. 5)  O2 SENSOR 

    If there are no possible causes remaining, view repair. 

    Repair 

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