P0131

P0131-O2 SENSOR 1/1 CIRCUIT LOW





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.

- When Monitored:
The diagnostic is carried out during a cold start and when the oxygen sensor is being used for closed-loop fuel control. For cold start - engine off time greater than 60 minutes, engine running for less than 15 seconds with battery voltage between 11.0 and 16.0 volts.

- Set Condition:
Cold start - the oxygen sensor signal voltage is below 0.05 Volts and greater than -1.00 Volts for a calibrated period of time. Closed-loop operation - if the closed-loop fuel trim is clamped rich and the sensor output voltage is below 0.05 Volts but greater than -1.00 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 BELOW 2.52 VOLTS
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. With a scan tool, read the 1/1 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. (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT




1. Turn the ignition off.
2. Disconnect the 1/1 O2 Sensor harness connector.
3. Ignition on, engine not running.
4. With a scan tool, monitor the O2 Sensor voltage.

Is the 1/1 O2 Sensor voltage above 4.8 volts?

Yes

- Go To 3

No

- Go To 5

3. O2 SENSOR




1. Measure the voltage on the (K902) O2 Return Upstream 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. (K902) O2 RETURN UPSTREAM CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Measure the resistance between ground and the (K902) O2 Return Upstream circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K902) O2 Return Upstream circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 7

5. (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Measure the resistance between ground and the (K41) O2 Sensor 1/1 Signal circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K41) O2 Sensor 1/1 Signal circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 6

6. (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO THE (K902) O2 RETURN UPSTREAM CIRCUIT




1. Measure the resistance between the (K41) O2 Sensor 1/1 Signal circuit and the (K902) O2 Return Upstream circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short between the (K902) O2 Return Upstream circuit and the (K41) O2 Sensor 1/1 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.

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