P2271
DTC P2271
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.
DTC Descriptors
DTC P2271
- HO2S Signal Stuck Rich Bank 1 Sensor 2
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,275 mV. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
Conditions for Running the DTC
* DTCs P0036, P0037, P0038, P0137, P0138, P0140, P0141, P0443, P0458, P0459, or P2232 are not set.
* The ignition 1 voltage is between 10-18 volts.
* The engine run time is greater than 5 minutes.
* The engine speed is between 1,100-2,500 RPM.
* The mass air flow (MAF) is between 5-20 g/s.
* The vehicle speed is between 50-120 km/h (31-75 mph).
* The fuel level is greater than 10 percent.
* The fuel system is in Closed Loop.
* The catalytic converter temperature is between 550-900°C (1,022-1,652°F).
* The DTCs run once per ignition cycle when the above conditions are met.
Conditions for Setting the DTC
* The ECM detects that the HO2S 2 voltage oscillations are faster than a calibrated value.
* DTC P2271 sets within 4 seconds when the above condition is met continuously, or within 50 seconds when the above condition is met cumulatively.
Action Taken When the DTC Sets
DTC P2271 is a Type B DTC.
Conditions for Clearing the DTC
DTC P2271 is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
* Heated Oxygen Sensor Wiring Repairs (Heated Oxygen Sensor Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning)for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify that no HO2S heater DTCs are set.
• If any HO2S heater DTCs are set, perform those diagnostics first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).
2. Engine idling, move the appropriate HO2S 2 harness connector and the engine control module (ECM) harness connector while monitoring the HO2S 2 voltage parameter with a scan tool. Verify that the HO2S parameter does not change abruptly while moving the related harnesses.
• If the HO2S parameter does change abruptly while moving the related harnesses repair the circuit as necessary.
3. Engine idling at operating temperature, observe the appropriate HO2S 2 parameter with a scan tool. The HO2S 2 value should change greater than 200 mV when the throttle is quickly cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM for 30 seconds.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF for 1 minute. Disconnect the harness connector at the appropriate HO2S.
2. Test for less than 5 ohm between the low reference circuit terminal A and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, verify the appropriate scan tool B52 HO2S parameter is approximately 450 mV.
• If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
• If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool HO2S parameter is less than 60 mV.
• If greater than the specified range, test the signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
5. Verify none of the following conditions exist:
* Rich fuel injectors-Refer to Fuel Injector Diagnosis (W/J39021 or W/Tech 2) (Fuel Injector Diagnosis (W/J39021 or W/Tech 2))Fuel Injector Diagnosis (W/CH47976) (Fuel Injector Diagnosis (W/CH47976))
* Water intrusion in the HO2S harness connector
* High fuel system pressure-Refer to Fuel System Diagnosis (Fuel System Diagnosis)
* Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Alcohol/Contaminants-In-Fuel Diagnosis)
* Exhaust restrictions
* Contaminated HO2S - Silicon
* An engine mechanical condition-Symptoms - Engine Mechanical (Symptoms - Engine Mechanical)
• If you find any of the above conditions, repair as necessary.
6. If all circuits test normal, replace the appropriate HO2S.
Repair Instructions
Caution: Refer to Heated Oxygen Sensor Resistance Learn Reset Caution (Heated Oxygen Sensor Resistance Learn Reset Caution).
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (Service and Repair)
* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming