P0138
P0138-O2 SENSOR 1/2 CIRCUIT HIGH
For a complete wiring diagram Refer to the Wiring Information.
- When Monitored:
Continuously with the engine running, no O2 sensor heater DTCs present, 1/2 Oxygen Sensor heater temperature within a specific range, and battery voltage greater than 10.4 volts.
- Set Condition:
The PCM detects that the 1/2 Oxygen Sensor voltage is greater than the maximum acceptable value for a specific amount of time, based on O2 sensor heater temperature. The DTC will set as Pending after one trip and Active after two trips. Three good trips to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
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.
1. 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 possible serious or fatal injury.
2. With a scan tool, select View DTCs.
Is the DTC Active at this time?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition Test.
2. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the C1 and C2 PCM harness connectors.
3. Disconnect the 1/2 O2 Sensor harness connector.
4. Turn the ignition on.
5. 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
- Repair the short to voltage in the (K141) O2 Sensor 1/2 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 3
3. (K904) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO VOLTAGE
1. 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 voltage in the (K904) O2 Return Downstream circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 4
4. O2 SENSOR
1. Turn the ignition off.
2. Connect the C1 and C2 PCM harness connectors.
3. Ignition on, engine not running.
4. With a scan tool, monitor the 1/2 O2 Sensor voltage.
5. 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
- Verify that there is good pin to terminal contact in the 1/2 O2 Sensor and Powertrain Control Module connectors. If OK, replace the 1/2 O2 Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain 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 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 PCM Pinout Box 8815 to perform diagnosis.
3. 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
- Go To 6
No
- Repair the open in the (K141) O2 1/2 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain 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 appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
Yes
- Go To 7
No
- Repair the open in the (K904) O2 Return Downstream circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
7. POWERTRAIN CONTROL MODULE (PCM)
1. 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).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the O2 Sensor and Powertrain Control Module connectors.
4. Search for any Technical Service Bulletins that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.