P0138
P0138-O2 SENSOR 1/2 CIRCUIT HIGH
For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.
- When Monitored:
Engine running, oxygen sensor at operating temperature (light-off time is 10 seconds), battery voltage between 11.0 and 16.0 volts
- Set Condition:
The oxygen sensor signal voltage is between 1.15 and 2.20 volts for a calibrated period of time. This is a two trip fault. Three good trips are required to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. O2 SENSOR ABOVE 3.7 VOLTS
NOTE: When only one O2 Sensor is shorted to voltage, the scan tool will display all O2 Sensor voltage readings at approximately 5.0 volts. When diagnosing this DTC, only diagnose the O2 Sensor that set the DTC.
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. With a scan tool, read the 1/2 O2 Sensor voltage.
Is the voltage above 3.7 volts?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Checking for an Intermittent DTC.
2. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
1. Start the engine and allow the engine to idle.
2. Disconnect the 1/2 O2 Sensor harness connector.
3. 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 the voltage above 0 volts?
Yes
- Repair the short to battery voltage in the (K141) O2 Sensor 1/2 Signal circuit.
- Perform the PCM Verification Test.PCM Verification Test
No
- Go To 3
3. (K904) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO BATTERY VOLTAGE
1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (K904) O2 Return Downstream circuit in the O2 Sensor harness connector.
Is there any voltage present?
Yes
- Repair the short to battery voltage in the (K904) O2 Return Downstream circuit.
- Perform the PCM Verification Test.PCM Verification Test
No
- Go To 4
4. O2 SENSOR
1. Turn the ignition off.
2. Connect the C1 PCM harness connector.
3. 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.
4. Ignition on, engine not running.
5. With a scan tool, monitor the 1/2 O2 Sensor voltage.
Is the voltage between 2.3 and 2.7 volts with the jumper wire installed?
Yes
- Replace the O2 Sensor.
- Perform the PCM Verification Test.PCM Verification Test
No
- Go To 5 NOTE: Remove the jumper wire before continuing.
5. (K141) O2 1/2 SIGNAL CIRCUIT OPEN
1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Measure the resistance of the (K141) O2 1/2 Signal circuit from the O2 Sensor harness connector to the C1 PCM harness connector.
Is the resistance below 5.0 ohms?
Yes
- Go To 6
No
- Repair the open in the (K141) O2 1/2 Signal circuit.
- Perform the PCM Verification Test.PCM Verification Test
6. (K904) O2 RETURN DOWNSTREAM CIRCUIT OPEN
1. Measure the resistance of the (K904) O2 Return Downstream circuit from the O2 Sensor harness connector to the C1 PCM harness connector.
Is the resistance below 5.0 ohms?
Yes
- Go To 7
No
- Repair the open in the (K904) O2 Return Downstream circuit.
- Perform the PCM Verification Test.PCM Verification Test
7. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
1. 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
- Repair as necessary.
- Perform the PCM Verification Test.PCM Verification Test
No
- Replace and program the Powertrain Control Module. Service and Repair
- Perform the PCM Verification Test.PCM Verification Test