P0139-O2 SENSOR 1/2 SLOW RESPONSE





For a complete wiring diagram Refer to Section 8W.


  • When Monitored:

    For six minutes after engine start up, vehicle speed between 20 and 55 MPH.

  • Set Condition:

    The O2 signal voltage does not switch lean or rich during monitoring for at least 2 to 4 minutes. Two Trip Fault. Three good trips to turn off the MIL.


Possible Causes
  
INTERMITTENT DTC
  
EXHAUST LEAK
  
(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO VOLTAGE
  
(K904) O2 1/2 RETURN CIRCUIT SHORTED TO VOLTAGE
  
(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO GROUND
  
(K904) O2 1/2 RETURN CIRCUIT SHORTED TO GROUND
  
(K141) O2 1/2 SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE
  
(K904) O2 1/2 RETURN CIRCUIT OPEN OR HIGH RESISTANCE
  
OXYGEN SENSOR 1/2
  
POWERTRAIN CONTROL MODULE (PCM)
  

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).


1.EXHAUST LEAK

NOTE: A thorough exhaust leak test must be completed before removing an O2 Sensor or any other part from the exhaust system. Do not remove any parts before an exhaust leak check has been completed.


NOTE: An exhaust leak may cause downstream fuel adaptives to rail out, resulting in a false 1/1 O2 Sensor failure.












Were any exhaust leaks found?

Yes


No
  • Go to 2

2.DTC IS ACTIVE

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


NOTE: It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.



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.




Is the status Active for this DTC?

Yes
  • Go to 3


No

3.(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO VOLTAGE






NOTE: Measure the voltage in reference to ground, not the (K904) O2 1/2 Return circuit.



Is the voltage above 5.2 volts?

Yes


No
  • Go to 4

4.(K904) O2 1/2 RETURN CIRCUIT SHORTED TO VOLTAGE








Is there any voltage present?

Yes


No
  • Go to 5

5.(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO GROUND






Is the resistance below 100 ohms?

Yes


No
  • Go to 6

6.(K904) O2 1/2 RETURN CIRCUIT SHORTED TO GROUND





Is the resistance below 100 ohms?

Yes


No
  • Go to 7

7.(K141) O2 1/2 SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE





Is the resistance below 5.0 ohms?

Yes
  • Go to 8


No

8.(K904) O2 1/2 RETURN CIRCUIT OPEN OR HIGH RESISTANCE





Is the resistance below 5.0 ohms?

Yes
  • Go to 9


No

9.OXYGEN SENSOR 1/2

NOTE: Prior to replacing the O2 sensor, verify that the correct part number is being used in order to prevent improper O2 heater control.







Were any problems found?

Yes


No