P2271

P2271-O2 SENSOR 1/2 SIGNAL STUCK RICH





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

Theory of Operation

The downstream O2 Sensor is located in the exhaust path behind the Catalytic Converter and is monitored for proper response to assure optimum Catalytic Converter efficiency. The downstream O2 Sensor response monitor is intended to diagnose a downstream O2 Sensor that is not moving or stuck in a voltage window and to insure accurate information for catalyst monitor diagnosis.

- 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 Powertrain Control Module (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. PCM Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. DIAGNOSTIC TROUBLE CODE (DTC) IS ACTIVE
1. 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 may result in possible serious or fatal injury.

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

2. With the scan tool, read the active DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. PCM Intermittent Condition Test.

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.

1. 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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the O2 Sensor 1/2 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 Sensor and the Powertrain Control Module connectors.
- Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module (PCM). Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.