For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provide an overview of each diagnostic category.

### DTC Descriptors

DTC P2270: HO2S Signal Stuck Lean Bank 1 Sensor 2
DTC P2272: HO2S Signal Stuck Lean Bank 2 Sensor 2

### Circuit Description

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 and stores the HO2S voltage information. The ECM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The ECM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

### Conditions for Running the DTC

• | Before the ECM can report DTC P2270 or P2272 failed, DTCs P0036, P0037, P0038, P0056, P0057, P0058, P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, P0393, P0443, P0458, and P0459 must run and pass.

• | DTCs P0461, P0462, P0463, P2066, P2067, and P2068 are not set.

• | The engine is operating.

• | The ignition voltage is greater than 10 volts.

• | The HO2S 2 is at operating temperature for greater than 10 seconds.

• | The long term fuel control is enabled.

• | The mass air flow (MAF) sensor is greater than 10 g/s.

• | The MAF sensor is between 6-33 g/s for greater than 3 seconds during the intrusive test.

• | DTC P2270 and P2272 run continuously once the above conditions are met for approximately 10 minutes when the fuel level is more than 12 percent.

• | DTC P2270 and P2272 run continuously once the above conditions are met for approximately 20 minutes when the fuel level is less 12 percent.

### Conditions for Setting the DTC

The ECM detects that the HO2S 2 voltage is less than 650 mV for greater than 100 seconds, then an intrusive test is performed. The ECM will enrich the fuel mixture up to 30 percent for 10 seconds. The DTC sets if ECM detects that the HO2S 2 voltage is remains less than 650 mV during the intrusive test for greater than 4 seconds or for a cumulative of 50 seconds.

### Action Taken when the DTC Sets

DTCs P2270 and P2272 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P2270 and P2272 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool DTC information. Verify that DTCs P0137, P0138, P0140, P0157, P0158, or P0160 are not set.

⇒ | If any of the listed DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Operate the engine above 1,200 RPM for 30 seconds, observe the HO2S voltage parameter. The reading should fluctuate above and below the range of 350-550 mV.
3. 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.

### Circuit/System Testing

1. Engine operating, move the related HO2S harnesses for the appropriate rear sensor between the HO2S harness connector and the engine control module (ECM) while monitoring the appropriate HO2S voltage parameter. 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.

2. Ignition OFF, disconnect the harness connector of the appropriate HO2S.
3. Ignition ON, verify that the HO2S parameter is between 350-500 mV.

⇒ | If less than 350 mV, test the signal circuit of the HO2S sensor for a short to ground. If the circuit/connections test normal, replace the ECM.

4. Verify that none of the following conditions exist:

• | Lean 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

• | Low fuel system pressure--Refer to Fuel System Diagnosis.

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

• | The vacuum hoses for splits, kinks, and proper connection

• | The air intake system after the mass air flow (MAF) sensor for vacuum leaks

• | Exhaust system leaks

• | Contaminated HO2S - Silicon

• | An engine mechanical condition. Refer to Symptoms - Engine Mechanical.

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

5. If all circuits/connections test normal, replace the applicable HO2S.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 2

• | Control Module References for engine control module replacement, setup, and programming