NGC

P0131-O2 SENSOR 1/1 CIRCUIT LOW





For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
With the engine running, battery voltage greater than 10.4 volts, and no O2 sensor heater DTCs present.

- Set Condition:
The PCM detects that the 1/1 Oxygen Sensor signal voltage is below approximately 1.5 volts for 2.8 seconds after engine startup. 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.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. DTC IS ACTIVE
Turn the ignition on.
With a scan tool, select View DTCs. Record DTC and Freeze Frame information.
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 personal injury or death.

With a scan tool, select View DTCs.
Is the DTC Active at this time?

Yes

- Go to 2

No

- Refer to the CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC

2. (K41) O2 1/1 SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the 1/1 Oxygen Sensor harness connector.
Turn the ignition on.
With a scan tool, read the 1/1 Oxygen Sensor voltage.
Is the 1/1 Oxygen Sensor voltage above 4.8 volts?

Yes

- Go to 3

No

- Go to 5

3. 1/1 OXYGEN SENSOR




Measure the voltage on the (K902) O2 Return (Up) circuit in the 1/1 Oxygen Sensor harness connector.
Is the voltage at 2.5 volts?

Yes

- Verify that there is good pin to terminal contact in the Oxygen Sensor and Powertrain Control Module connectors. If OK, replace the 1/1 O2 Sensor.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 4

4. (K902) O2 RETURN (UP) CIRCUIT SHORTED TO GROUND




Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) harness connector.
Measure the resistance between ground and the (K902) O2 Return (Up) circuit in the 1/1 Oxygen Sensor harness connector.
Is the resistance below 100 ohms?

Yes

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

No

- Go to 5

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




Measure the resistance between ground and the (K41) O2 1/1 Signal circuit in the 1/1 Oxygen Sensor harness connector.
Is the resistance below 100 ohms?

Yes

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

No

- Go to 6

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




Measure the resistance between the (K41) O2 1/1 Signal circuit and the (K902) O2 Return (Up) circuit in the 1/1 Oxygen Sensor harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short between the (K41) O2 1/1 Signal circuit and the (K902) O2 Return (Up) circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 7

7. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the 1/1 Oxygen Sensor 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.
Verify that there is good pin to terminal contact in the Oxygen Sensor and Powertrain Control Module connectors.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

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