P0157

P0157-O2 SENSOR 2/2 CIRCUIT LOW





For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
Engine running for less than 30 seconds and the O2 Sensor Heater Temperature is less than 251° C (484° F) with battery voltage greater 10.99 volts.

- Set Condition:
The oxygen sensor signal voltage is below 2.5196 volts for 3 seconds after starting engine. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

Diagnostic Test

1. O2 SENSOR BELOW 2.52 VOLTS
Start the engine.
Allow the engine to reach normal operating temperature.
With a scan tool, read the 2/2 O2 Sensor voltage.
Is the voltage below 2.52 volts?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Checking for an Intermittent DTC.

2. (K243) O2 2/2 SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the 2/2 O2 Sensor harness connector.
Ignition on, engine not running.
With a scan tool, monitor the 2/2 O2 Sensor voltage.
Is the O2 Sensor voltage above 4.8 volts?

Yes

- Go To 3

No

- Go To 5

3. O2 SENSOR




Measure the voltage on the (K908) O2 Return Downstream circuit in the O2 Sensor harness connector.
Is the voltage at 2.5 volts?

Yes

- Replace the O2 Sensor.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 4

4. (K908) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO GROUND




Turn the ignition off.
Disconnect the C12 PCM harness connector.
Measure the resistance between ground and the (K908) O2 Return Downstream circuit in the O2 Sensor harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K908) O2 Return Downstream circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 7

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




Turn the ignition off.
Disconnect the C1 PCM harness connector.
Measure the resistance between ground and the (K243) O2 2/2 Signal circuit in the O2 Sensor harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K243) O2 2/2 Signal circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 6

6. (K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO THE (K908) O2 RETURN DOWNSTREAM CIRCUIT




Measure the resistance between the (K243) O2 2/2 Signal circuit and the (K908) O2 Return Downstream circuit in the O2 Sensor harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short between the (K908) O2 Return Downstream circuit and the (K243) O2 2/2 Signal circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 7

7. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

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.Testing and Inspection
- Perform the PCM Verification Test.PCM Verification Test