The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the low reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The ECM monitors the HO2S voltage to determine if the signal voltage goes below a predetermined threshold within a certain amount of time. If the ECM determines that the signal voltage remains above a threshold, the ECM commands a lean condition. If the signal voltage does not go below the threshold within a certain amount of time after commanding the system lean, this DTC sets.

The ECM monitors the HO2S voltage during fuel cut-off. If the ECM determines that the signal voltage is greater than a predetermined voltage during fuel cut-off, this DTC sets.

If the ECM detects that the HO2S 2 voltage is greater than a range of 582-640 mV for greater than 100 seconds, then an intrusive test is performed. The ECM will lean the fuel mixture up to -7 percent and then wait for 10 seconds at -7 percent. If the ECM detects that the HO2S 2 voltage is still greater than the specified range, the ECM then tests the HO2S 2 at the next decel fuel cut-off. If the ECM detects the HO2S 2 voltage is greater than 140 mV after 4 seconds in decel fuel cut-off, this DTC sets.

DTC  P2271 is a Type B DTC.

DTC  P2271 is a Type B DTC.

The following table illustrates the ECM connector locations:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Important: Inspect the heated oxygen sensor (HO2S) for being secure before proceeding with this DTC. A sensor that is loose could cause this DTC to set.

1. Ignition ON, observe the scan tool DTC information. Verify DTCs P0137, P0138, or P0140 are not set.

⇒	If any of the above DTCs are set, refer to DTC P0137, P0138, or P0140 for further diagnosis.

2. 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 are captured in the Freeze Frame/Failure Records Data List.

1. Engine idling, raise the engine speed to greater than 1,200 RPM for greater than 30 seconds. Observe the scan tool HO2S 2 voltage parameter. Verify the parameter is less than 1,050 mV.

⇒	If greater than the specified range, test the HO2S 2 high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

2. Move the related HO2S 2 harnesses between the HO2S harness connector and the engine control module (ECM). Observe the scan tool HO2S 2 voltage parameter. Verify the parameter does not change abruptly.

⇒	If the parameter changes abruptly, repair the harness as necessary.

3. Verify that none of the following conditions exist:

•	Collapsed air intake duct

•	Restricted air filter element

•	Mass air flow (MAF) sensor for foreign objects

•	Rich fuel injectors--Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2

•	Water intrusion in the HO2S harness connector

•	HO2S wiring harness damage

•	Incorrect fuel system pressure--Refer to Fuel System Diagnosis

•	Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis

•	Exhaust leaks near the HO2S--Refer to Exhaust Leakage

•	Excessive fuel in the crankcase. Change the oil as necessary

⇒	If you find any of the above conditions, repair as necessary.

4. If all conditions test normal, replace the HO2S 2.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.