P0137-O2 SENSOR 1/2 CIRCUIT LOW
For a complete wiring diagram Refer to Section 8W.
- When Monitored:
With the engine running for less than 30 seconds, the Oxygen Sensor 1/2 heater temperature less than 251° C (484° F), and battery voltage greater than 10.4 volts.
- Set Condition:
The PCM detects that the Oxygen Sensor 1/2 signal voltage is below 2.5196 volts for 6 seconds after engine startup. One Trip Fault. Three good trips to turn off the MIL.
| Possible Causes |
| (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO GROUND |
| (K904) O2 1/2 RETURN CIRCUIT SHORTED TO GROUND |
| (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 1/2 RETURN CIRCUIT |
| (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K299) O2 1/2 HEATER CONTROL CIRCUIT |
| OXYGEN SENSOR 1/2 |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE).
Diagnostic Test
1. OXYGEN SENSOR 1/2 VOLTAGEStart the engine and allow it to reach normal 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, monitor the Oxygen Sensor 1/2 voltage.
Is the voltage less than 2.52 volts?
Yes
- Go to 2
No
- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
2. (K141) O2 1/2 SIGNAL CIRCUIT VOLTAGE
Turn the ignition off.
Disconnect the Oxygen Sensor 1/2 harness connector.
Turn the ignition on.
With a scan tool, monitor the Oxygen Sensor 1/2 voltage.
Is the Oxygen Sensor 1/2 voltage above 4.8 volts?
Yes
- Go to 3
No
- Go to 5
3. OXYGEN SENSOR 1/2
Measure the voltage on the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.
Is the voltage at 2.5 volts?
Yes
- Replace the Oxygen Sensor 1/2.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go to 4
4. (K904) O2 1/2 RETURN CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) harness connector.
Measure the resistance between ground and the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the (K904) O2 1/2 Return circuit for a short to ground.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go to 8
5. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K141) O2 1/2 Signal circuit in the Oxygen Sensor 1/2 harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the (K141) O2 1/2 Signal circuit for a short to ground.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go to 6
6. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 1/2 RETURN CIRCUIT
Measure the resistance between the (K141) O2 1/2 Signal circuit and the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the short between the (K904) O2 1/2 Return circuit and the (K141) O2 1/2 Signal circuit.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go to 7
7. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K299) O2 1/2 HEATER CONTROL CIRCUIT
Measure the resistance between the (K141) O2 1/2 Signal circuit and the (K299) O2 1/2 Heater Control circuit in the Oxygen Sensor 1/2 harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the short between the (K299) O2 1/2 Heater Control circuit and the (K141) O2 1/2 Signal circuit.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go to 8
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
- Repair as necessary.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).