2007 Compass Patriot MK Factory Service Manual 9 - ENGINE

P0138-O2 SENSOR 1/2 CIRCUIT HIGH





For a complete wiring diagram Refer to Section 8W.



Possible Causes
  
(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 THE (K299) O2 1/2 HEATER CONTROL CIRCUIT
  
(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).



Diagnostic Test

1. OXYGEN SENSOR 1/2 VOLTAGE

Start the engine and allow it to reach operating temperature.

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, read the Oxygen Sensor 1/2 voltage.

Is the voltage greater than 3.9 volts?

Yes


No

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



Start the engine and allow it to idle.
Disconnect the Oxygen Sensor 1/2 harness connector.
Measure the voltage on the (K141) O2 1/2 Signal circuit in the Oxygen Sensor 1/2 harness connector.

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

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



Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) harness connector.
Turn the ignition on.
Measure the voltage on the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.

Is there any voltage present?

Yes


No

4. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K299) O2 1/2 HEATER CONTROL CIRCUIT



Turn the ignition off.
Measure the resistance between the (K141) O2 1/2 Signal circuit and the (K299) O2 1/2 Heater Control circuit the Oxygen Sensor 1/2 harness connector.

Is the resistance below 100.0 ohms?

Yes


No

5. OXYGEN SENSOR 1/2



Turn the ignition off.
Connect the Powertrain Control Module (PCM) harness connector.
Connect a jumper wire between the (K141) O2 1/2 Signal circuit and the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.
Turn the ignition on.
With a scan tool, monitor the Oxygen Sensor 1/2 voltage.

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

Yes


No

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



Turn the ignition off.
If necessary, remove the jumper wire from between the (K141) O2 1/2 Signal circuit and the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.
Disconnect the Powertrain Control Module (PCM) harness connector.
Measure the resistance of the (K141) O2 1/2 Signal circuit between the Oxygen Sensor 1/2 harness connector to the Powertrain Control Module (PCM) harness connector.

Is the resistance below 5.0 ohms?

Yes


No

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



Measure the resistance of the (K904) O2 1/2 Return circuit between the Oxygen Sensor 1/2 harness connector to the Powertrain Control Module (PCM) harness connector.

Is the resistance below 5.0 ohms?

Yes


No

8. POWERTRAIN CONTROL MODULE (PCM)

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor 1/2 and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Refer to any Technical Service Bulletins that may apply.

Were any problems found?

Yes


No