NGC

P2271-O2 SENSOR 1/2 SIGNAL STUCK RICH





For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
With the engine running, vehicle speed above 96 kph (60 mph), throttle open for a minimum of 120 seconds, ECT greater than 70 C (158 F), catalytic converter temperature greater than 600 C (1112 F), and downstream oxygen sensor in a rich state. During a decel fuel shutoff event, the downstream oxygen sensor should switch from rich to lean within a specific time.

- Set Condition:
The PCM monitors the downstream O2 sensor. If the PCM does not detect a rich to lean switch within a specific time during a decel fuel shutoff event, the monitor will fail. 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. DTC IS ACTIVE
Start the engine and allow it to reach operating temperature.

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.

NOTE: It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.

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. CHECKING THE OXYGEN SENSOR OPERATION

NOTE: Check for signs of contaminants that may have damaged the O2 Sensor, such as contaminated fuel, unapproved silicone, oil and coolant.

Perform the diagnostic procedure for *CHECKING THE OXYGEN SENSOR OPERATION. Checking the Oxygen Sensor Operation
Were any problems found?

Yes

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

No

- Go to 3

3. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the 1/2 O2 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.
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