P0151

P0151-O2 SENSOR 2/1 CIRCUIT LOW





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

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

- Set Condition:
The Powertrain Control Module (PCM) detects that the 2/1 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. 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 hand 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. (K43) O2 2/1 SIGNAL CIRCUIT
1. Turn the ignition off.
2. Disconnect the 2/1 Oxygen Sensor harness connector.
3. Turn the ignition on.
4. With a scan tool, read the 2/1 Oxygen Sensor voltage.

Is the 2/1 Oxygen Sensor voltage above 4.8 volts?

Yes

- Go To 3

No

- Go To 5

3. 2/1 OXYGEN SENSOR




1. Measure the voltage on the (K902) O2 Return (Up) circuit in the 2/1 Oxygen Sensor harness connector.

Is the voltage between 2.40 and 2.60 volts?

Yes

- Replace the 2/1 Oxygen Sensor.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Go To 4

4. (K902) O2 RETURN (UP) 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 (K902) O2 Return (Up) circuit in the 2/1 Oxygen Sensor harness connector.

Is the resistance below 100 Ohms?

Yes

- Repair the (K902) O2 Return (Up) circuit for a short to ground.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Go To 5

5. (K43) O2 2/1 SIGNAL CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (K43) O2 2/1 Signal circuit in the 2/1 Oxygen Sensor harness connector.

Is the resistance below 100 Ohms?

Yes

- Repair the (K43) O2 2/1 Signal circuit for a short to ground.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Go To 6

6. (K43) O2 2/1 SIGNAL CIRCUIT SHORTED TO THE (K902) O2 RETURN (UP) CIRCUIT




1. Measure the resistance between the (K43) O2 2/1 Signal circuit and the (K902) O2 Return (Up) circuit in the 2/1 Oxygen Sensor harness connector.

Is the resistance below 100 Ohms?

Yes

- Repair the short between the (K43) O2 2/1 Signal circuit and the (K902) O2 Return (Up) circuit.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.

No

- Go To 7

7. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the 2/1 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.
4. Perform 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.