For 1990-2009 cars

### 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. The ECM test for the following conditions:

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

• | The ECM monitors the HO2S voltage during power enrichment. If the ECM determines that the signal voltage is less than a predetermined voltage during power enrichment, this DTC sets.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2270 HO2S Signal Stuck Lean Bank 1 Sensor 2

DTC P2272 HO2S Signal Stuck Lean Bank 2 Sensor 2

### Conditions for Running the DTC

• | Before the ECM can report DTC P2270 or P2272 failed, DTC P0036, P0037, P0038, P0056, P0057, P0058, P137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0342, P0343, P0367, P0368, P0366, P0443, P0451, P0452, P0453, P0458, and P0459 must run and pass.

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

• | The engine is running.

• | The rear HO2S are at operating temperature for more than 10 seconds.

• | The mass air flow (MAF) sensor flow is more than 9.72 g/s.

• | The MAF sensor flow is 5.6-33 g/s for more than 3 seconds during the intrusive test.

• | The ignition 1 voltage is more than 10.5 volts.

• | The rear HO2 S closed loop control is enabled.

• | The engine decel fuel cut-off state is not detected.

• | The post oxygen sensors adjust--express diluted correction.

• | The post oxygen sensors adjust--express rich correction.

• | The post oxygen sensors adjust--hesitation correction.

• | After decel fuel cut-off is invalid, a malfunction exists in the post oxygen sensors deterioration diagnosis.

• | DTC P2270 and P2272 runs continuously once the above conditions have been met for approximately 10 minutes.

### Conditions for Setting the DTC

If the ECM detects that the rear HO2S voltage is less than 0.582-0.661 volts for more than 100 seconds, then an intrusive test is performed. The ECM enriches the fuel mixture up to predetermined value with the change rate of 0.017 per second and then wait for 10 seconds at the value. If the ECM detects that the HO2S voltage is still less than 0.582 0.661 volts, this DTC sets.

### Action Taken When the DTC Sets

• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail

• | A current DTC, last test failed, clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Clear the MIL and the DTC with a scan tool.

### Diagnostic Aids

• | Use the J 35616 for any test that requires probing the ECM harness connector or a component harness connector.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views .

• | A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a lean condition.

• | For an intermittent, refer to Intermittent Conditions .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step determines if a condition exists.

2. This step is testing for a rear HO2S sensor circuit condition. A circuit condition sets this DTC.

3. This step is testing for an intermittent circuit inspect the HO2S circuits for an intermittent circuit condition.

### DTC P2270 or P2272

Step | Action | Values | Yes | No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Allow the engine to reach operating temperature.
2. Operate the vehicle within the parameters specified in Conditions for Running the DTC.
3. Observe the diagnostic trouble code (DTC) information with a scan tool.

Did DTC P2270 or DTC P2272 fail this ignition?

--

Go to Step 4

Go to Step 3

3 |

1. Observe the Freeze Frame and/or the Failure Records data for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure Records data.

--

Go to Step 4

Go to Diagnostic Aids

4 | Is DTC P0137, P0138, P0140, P0157, P0158, or P0160 also set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 5
5 |

1. Operate the engine above 1,200 RPM for 30 seconds.
2. Observe the appropriate rear heated oxygen sensor (HO2S) voltage with a scan tool.

Is the voltage greater than the specified value?

60 mV

Go to Step 8

Go to Step 6

6 |

1. Turn OFF the ignition.
2. Disconnect the appropriate HO2S.
3. Turn the ignition switch to ON position, with the engine OFF.
4. Observe the HO2S voltage parameter with a scan tool.

Is the voltage within the specified range?

350 - 550 mV

Go to Step 12

Go to Step 7

7 | Test the appropriate HO2S signal circuit for a short to ground. refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 13
8 | Move the related HO2 S harnesses for the rear sensor between the HO2 S harness connector and the engine control module (ECM) while monitoring the appropriate | -- | Go to Step 14 | Go to Step 9
9 |

1. Turn OFF the ignition.
2. Disconnect the appropriate HO2S.
3. Inspect the rear HO2S for the following conditions:

• | Damaged wiring between the HO2S and the ECM - An intermittent circuit condition may cause this DTC to set.

• | Terminal corrosion or water intrusion in the HO2S harness connector.

• | The correct terminal tension

• | The HO2S is securely installed.

• | Any exhaust leaks - Refer to Symptoms - Engine Exhaust

--

Go to Step 17

Go to Step 10

10 | Inspect for the following conditions:

• | For splits, kinks, and proper connections of the vacuum hoses - Refer to Emission Hose Routing Diagram

• | The crankcase ventilation valve and system for leaks

• | Contaminated fuel - refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | The engine control grounds for being clean, tight, and in the correct locations.

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

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

Did you find and correct the condition?

--

Go to Step 17

Go to Step 11

11 | Important: When you have completed the fuel system diagnosis, return to this diagnostic. Test the fuel system for operating lean. Refer to Fuel System Diagnosis . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 12
12 | Test for shorted terminals and for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15
13 | Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16
14 | Repair the circuit if necessary. Refer to Wiring Repairs . Did you complete the repairs? | -- | Go to Step 17 | --
15 | Replace the HO2S. Refer to the appropriate procedure:

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 2

--

Go to Step 17

--

16 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming . Did you complete the replacement? | -- | Go to Step 17 | --
17 |

1. Clear any DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 2

Go to Step 18

18 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic System Check - Vehicle | System OK