For 1990-2009 cars

### Circuit Description

The powertrain control module (PCM) supplies a bias voltage of about 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the HO2S low reference circuits. When measured with a 10-megaohm digital voltmeter, the voltage may read as low as 350 mV. The oxygen sensor signal varies from about 800 mV when the exhaust is rich, to about 50 mV when the exhaust is lean. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for a rich or a lean condition by decreasing or increasing the injector pulse width as necessary. If the HO2S 1 voltage remains excessively high for an extended period of time, DTC P0132 will set.

### Conditions for Running the DTC

There are no active diagnostic trouble codes (DTCs) of any of the following types present:

• | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201-P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.

• | The system voltage is more than 9 volts.

• | The Closed Loop commanded air-to-fuel ratio is between 12-16.5.

• | The throttle angle is between 3-35 percent .

### Conditions for Setting the DTC

• | The HO2S 1 signal voltage remains above 975 mV during normal Closed Loop operation.

| OR

• | The HO2S 1 signal voltage remains above 200 mV during deceleration fuel mode operation

• | The above conditions are present for up to 50 seconds.

### 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 failure. 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 3 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

Notice: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:

• | The PCM harness connectors

• | The electrical center fuse/relay cavities

• | The component terminals

• | The component harness connector

Using this kit will prevent damage caused by the improper probing of connector terminals.

Check the following items:

• | The fuel pressure--The system will go rich if pressure is too high. The PCM can compensate for some increase. However, if the fuel pressure is too high, DTC P0132 may be set. Refer to DTC P0132 .

• | The fuel injectors--Refer to Fuel Injector Balance Test with Special Tool .

• | Inspect the evaporative emission (EVAP) canister for fuel saturation. If the canister is full of fuel, inspect the canister and hoses.

• | Disconnect the mass air flow (MAF) sensor and see if rich condition is corrected. If so, replace the MAF sensor. Refer to Mass Airflow Sensor Replacement .

• | Test for a leaking fuel pressure regulator diaphragm by checking the vacuum line to the regulator for the presence of fuel.

• | An intermittent throttle position (TP) sensor output will cause the system to go rich due to a false indication of the engine accelerating.

• | A shorted heated oxygen sensor (HO2S)--If the HO2S is internally shorted, the HO2S voltage displayed on the scan tool will be more than 1.0 volt. Disconnect the affected HO2S and jumper the HO2S low reference circuit to ground with the key ON , and the engine OFF. If the displayed HO2S voltage changes from more than 1000 mV to approximately 450 mV, replace the HO2S. Silicon contamination of the HO2S can also cause a high HO2S voltage to be indicated. This condition is indicated by a powdery white deposit on the portion of the HO2S that is exposed to the exhaust stream. If you notice contamination, replace the affected HO2S. Refer to Heated Oxygen Sensor 1 Replacement or Heated Oxygen Sensor 2 Replacement .

• | An open HO2S high signal or low reference circuit or inoperative HO2S--A poor connection or an open in the HO2S high signal or low reference circuit can cause the DTC to set during deceleration fuel mode. An HO2S which is inoperative and not allowing a full voltage swing between the rich and lean thresholds can also cause this condition. Operate the vehicle while monitoring the HO2S voltage with a scan tool. If the HO2S voltage is limited within a range of 300-600 mV, check the HO2S high signal and low reference circuit wiring and the associated terminal connections. If the wiring and connections are OK, replace the HO2S. Refer to Heated Oxygen Sensor 1 Replacement or Heated Oxygen Sensor 2 Replacement .

If the problem is intermittent, refer to Intermittent Conditions .

Important: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

Check for the following conditions:

• | Poor terminal connection--Inspect the harness connectors for the following conditions:

- | Backed out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal to wire connections--Use a corresponding mating terminal in order to test for proper tension.

• | A damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault.

• | PCM and engine grounds for clean and secure connections--If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

### Test Description

The number below refers to step number on the diagnostic table.

1. This DTC failing during deceleration fuel mode operation, when the vehicle speed is more than 40 km/h (25 mph) and the TP angle is less than 3 percent, may indicate a condition described in Diagnostic Aids. If this DTC test passes while the Failure Records conditions are being duplicated, an intermittent condition is indicated. Review the Failure Records vehicle mileage since the diagnostic test last failed. This may help to determine how often the condition that caused the DTC to be set occurs.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Allow the engine to idle until the normal operating temperature is reached.
2. With a scan tool, observe the HO2S voltage for the sensor that applies to this DTC.

Is the HO2S voltage less than the value specified?

975 mV

Go to Step 3

Go to Step 4

3 | The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:

• | A HO2S high signal wire intermittently shorted to engine ground or to the HO2S low reference circuit

• | HO2S connector water intrusion

• | Silicon contamination of the HO2S

• | An intermittently rich engine condition caused by one of the following conditions:

- | An EVAP canister purge system malfunction

- | Fuel contamination of the engine oil

- | Incorrect fuel pressure

- | Leaking fuel pressure regulator

- | Rich fuel injectors

- | An inaccurate MAF sensor

• | A rich engine condition during DFCO operation .

Repair any of the above or similar engine conditions as necessary.

Did you find and correct the condition?

--

Go to Step 10

Go to Diagnostic Aids

4 |

1. Turn OFF the ignition.
2. Disconnect the HO2S connector for the sensor that applies to this DTC.
3. Jumper the HO2S low reference circuit terminal on the engine harness side to a known good ground.
4. Turn ON the ignition, with the engine OFF.
5. With a scan tool, observe the HO2S voltage for the sensor that applies to this DTC.

Is the HO2S voltage within the specified value range?

351-551 mV

Go to Step 5

Go to Step 6

5 | The HO2S is detecting a rich exhaust condition or may be contaminated. Check for one of the following conditions:

• | Water intrusion in HO2S connector

• | Silicon contamination of the HO2S

• | Fuel contamination in the engine oil

• | An EVAP canister purge system malfunction

• | Incorrect fuel pressure

• | Rich fuel injectors

• | An inaccurate MAF sensor

Important: If a rich engine condition was repaired, inspect the engine oil for fuel contamination and replace the engine oil as necessary.

Repair any of the above or similar engine conditions as necessary.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

6 |

1. Turn OFF the ignition.
2. Remove the jumper from the HO2S low reference circuit terminal.
3. Disconnect the PCM connector that contains the HO2S high signal circuit.
4. Turn ON the ignition, with the engine OFF.
5. Use a DMM in order to measure the voltage between the PCM connector terminal for the HO2S high signal on the harness side and a ground.

Does the voltage measure greater than the specified value?

20 mV

Go to Step 7

Go to Step 9

7 | Repair the short to voltage in the HO2S high signal circuit . Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 10 | --
8 | Important: Before replacing a contaminated HO2S, determine and repair the cause of the contamination. Replace the HO2S. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
9 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
10 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 11

Go to Step 2

11 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK