P2271
DTC P2271 or P2273
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
DTC P2273
- HO2S Signal Stuck Rich Bank 2 Sensor 2
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The control module supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the control module operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below the bias voltage. A high HO2S voltage indicates a rich exhaust stream. A low HO2S voltage indicates a lean exhaust stream.
Conditions for Running the DTC
* Before the ECM can report DTC P2271, or P2273 failed, DTCs P013A, P013C, P013E, P014A, P2270, and P2272 must run and pass.
* DTC P0036, P0037, P0038, P0137, P0138, P0140, P0141, P0443, P0458, P0459 or P2232 is not set.
* The ignition voltage is between 10-32 volts.
* The engine speed is between 500-5,000 RPM.
* The mass air flow (MAF) is between 3-50 g/s.
* The vehicle speed is between 24-132 km/h (15-82 mph).
* The fuel level is greater than 10 percent.
* The fuel system is in Closed Loop.
* The engine run time is equal to or more than 5 minutes.
* The accelerator pedal position (APP) is steady.
* The torque converter clutch is TCC is applied.
* The DTCs run once per ignition cycle, during decel fuel cut-off, when the above conditions are met.
Conditions for Setting the DTC
P2271
The ECM does not detect an HO2S voltage less than 150 mV before accumulated mass air flow exceeds a calibrated value.
P2273
The ECM does not detect an HO2S voltage less than 100 mV before the accumulated mass air flow exceeds a calibrated value.
Action Taken When the DTC Sets
DTCs P2271 or P2273 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P2271 or P2273 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics (LS3) [1][2]Electrical DiagramsEngine Controls Schematics (LS7) [1][2]Electrical DiagramsEngine Controls Schematics (LS9) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 5 Bow Lowered Switch (CM7)
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 Control Module References 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 scan tool HO2S 2 voltage parameter. Verify that the HO2S parameter does not change abruptly while moving the related harnesses.
• If the HO2S voltage parameter does change abruptly while moving the related harnesses repair the circuit as necessary.
3. Engine idling at operating temperature, observe the appropriate scan tool HO2S voltage parameter. Verify the following:
* The HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fueling changes.
* The HO2S 2 value should fluctuate at less than 380 mV or greater than 520 mV. The values should not remain within 380 mV and 520 mV.
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
Note: All modules must be powered down or misdiagnosis may result.
1. Ignition OFF, disconnect the harness connector at the appropriate B52 Heated Oxygen Sensor.
2. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes, test for less than 5 ohms 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 HO2S voltage 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 K20 Engine Control Module.
• If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
4. Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool HO2S voltage 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 K20 Engine Control Module.
5. Verify none of the following conditions exist:
* Rich fuel injectors-Refer to Fuel Injector Diagnosis (CH47976) Fuel Injector Diagnosis (CH47976)Fuel Injector Diagnosis (J39021 or Scan Tool) Fuel Injector Diagnosis (J39021 or Scan Tool)
* Water intrusion in the HO2S harness connector
* High fuel system pressure-Refer to Fuel System Diagnosis (LS9) Fuel System DiagnosisFuel System Diagnosis (LS3 or LS7) Fuel System Diagnosis
* Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis Testing and Inspection
* Fuel saturation of the evaporative emission (EVAP) canister
• If you find any of the above conditions, repair as necessary.
6. If all circuits test normal, replace the appropriate B52 Heated Oxygen Sensor.
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 Heated Oxygen Sensor Replacement - Bank 1 Sensor 2
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 Heated Oxygen Sensor Replacement - Bank 2 Sensor 2
* Control Module References Control Module References for ECM replacement, setup, and programming