P0157

P0157-O2 SENSOR 2/2 CIRCUIT LOW







- When Monitored:
With the engine running for less than 30 seconds, the 2/2 Oxygen Sensor heater temperature less than 251 C (484 F), and battery voltage greater than 10 volts.

- Set Condition:
The Powertrain Control Module (PCM) detects that the 2/2 Oxygen Sensor signal voltage is below 2.5196 volts for 6 seconds after engine startup. One Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DTC IS ACTIVE
1. Turn the ignition on.
2. With a scan tool, select View DTCs. Record DTC and Freeze Frame information.
3. 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.

4. With a scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. Checking for an Intermittent DTC.

2. (K243) O2 2/2 SIGNAL CIRCUIT VOLTAGE
1. Turn the ignition off.
2. Disconnect the 2/2 Oxygen Sensor harness connector.
3. Turn the ignition on.
4. With a scan tool, monitor the 2/2 Oxygen Sensor Volts.

Is the voltage above 4.8 volts?

Yes

- Go To 3

No

- Go To 5

3. 2/2 OXYGEN SENSOR RETURN CIRCUIT VOLTAGE




1. Measure the voltage on the (K904) O2 1/2 Return circuit in the 2/2 Oxygen Sensor harness connector.

Is the voltage between 2.475 and 2.525 volts?

Yes

- Go To 7

No

- Go To 4

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




1. Turn the ignition off.
2. Disconnect the Powertrain Control Module (PCM) harness connector.
3. Measure the resistance between ground and the (K904) O2 1/2 Return circuit in the 2/2 Oxygen Sensor 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. PCM Verification Test.

No

- Go To 8

5. (K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (K243) O2 2/2 Signal circuit in the 2/2 Oxygen Sensor harness connector.

Is the resistance below 100 Ohms?

Yes

- Repair the (K243) O2 2/2 Signal circuit for a short to ground.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Go To 6

6. (K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 1/2 RETURN CIRCUIT




1. Measure the resistance between the (K243) O2 2/2 Signal circuit and the (K904) O2 1/2 Return circuit in the 2/2 Oxygen Sensor harness connector.

Is the resistance below 100 Ohms?

Yes

- Repair the short between the (K904) O2 1/2 Return circuit and the (K243) O2 2/2 Signal circuit.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Go To 8

7. 2/2 OXYGEN SENSOR
1. Turn the ignition off.
2. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the 2/2 Oxygen Sensor and the Powertrain Control Module (PCM).
3. Look for any chafed, pierced, pinched, or partially broken wires.
4. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Replace the 2/2 Oxygen Sensor.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

8. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the 2/2 Oxygen Sensor 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 related connectors.
4. Search for any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM VERIFICATION TEST. PCM Verification Test.