For 1990-2009 cars
HO2S Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The heated oxygen sensor (HO2S) produces a voltage that varies between 100 mV and 900 mV under normal operating conditions. The powertrain control module (PCM) monitors this voltage and determines if the exhaust is indicating a lean or rich fuel mixture. If the voltage input at the PCM is about 100 mV the fuel mixture is lean, and if the voltage input is about 900 mV the fuel mixture is rich. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing fuel injector pulse width as necessary. If the HO2S 1 voltage remains excessively high for an extended period of time, a DTC P0132 will be set.

### Conditions for Running the DTC

• | The barometric pressure (BARO) is more than 75 kPa.

• | The engine coolant temperature (ECT) is between -8°C and +110°C (18°F-230°F).

• | The intake air temperature (IAT) is more than -8°C (+18°F) at engine start up.

• | The vehicle speed is more than 56 km/h (35 mph) for 2 minutes and then idled for 1 minute.

### Conditions for Setting the DTC

The minimum voltage is more than 300 mV.

OR:

The maximum average voltage is at least 740 mV and the minimum average voltage is at least 330 mV.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns off after 3 consecutively passing trips without a fault present.

• | A history DTC will clear after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

A DTC P0132 is more likely to set during city driving. Avoid operating the vehicle on the highway when validating a DTC P0131.

Check for any of the following conditions:

• | If any DTCs other than fuel trim (P0171, P0172), misfire (P0300 to P0304), EGR (P0400) and HO2S 1 (P0131 to P0134) are set, diagnosis those DTCs first.

• | Before replacement of the HO2S, check the HO2S ground circuit for a possible open or short.

• | The fuel pressure. The system will go rich if the fuel pressure is too high, and DTC P0132 may be set.

• | Check the EVAP canister for fuel saturation.

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

• | A shorted HO2S. If the HO2S is internally shorted to voltage, the HO2S reading displayed on the scan tool will be more than 1 volt. Water contamination of the HO2S can cause a high HO2S voltage to be indicated. If DTC P0132 occurs when driving through standing water or when operating the vehicle in wet driving conditions, replace the HO2S if the sensor is adversely affected by moisture.

If a DTC P0132 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool clear DTC information function. Road test the vehicle while monitoring the DTC P0132 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0132 appears in the Not Ran Since Code Cleared list, the P0132 diagnostic has not yet run. When the DTC P0132 does not appear in the Not Ran Since Code Cleared list, the P0132 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P0132 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a problem in the HO2S 1 electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Any backed-out terminals

• | Any improper mating of terminals

• | Any broken electrical connector locks

• | Any improperly formed or damaged terminals

• | Any faulty terminal-to-wire connections

• | Any physical damage to the wiring harness

• | A broken wire inside the insulation

• | Any corrosion of the electrical connections, the splices, or the terminals

If the DTC P0132 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

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

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step determines if the fault is present. The vehicle must be at operating temperature.

3. This step checks whether the malfunction that caused the DTC P0132 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool clear DTC information function, the DTC P0132 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0132 appears in the Not Ran Since Code Cleared list, the P0132 diagnostic has not yet run. When DTC P0132 does not appear in the Not Ran Since Code Cleared list, the P0132 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the P0132 diagnostic has passed. DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

4. This step checks for an open in the HO2S 1 ground circuit.

5. This step checks for a short in the HO2S 1 signal circuit.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any HO2S 1 DTCs set other than DTC P0131 and DTC P0132? | -- | Go to Diagnostic Trouble Code (DTC) List | Go to Step 3
3 |

1. Start the engine.
2. Run the engine until the engine reaches a normal operating temperature.
3. Increase the engine speed to 2,000 RPM for 1 minute.
4. Monitor the HO2S 1 voltage with a scan tool.

Does the HO2S 1 voltage switch below and above the specified value?

300 mV - 600 mV

Go to Step 4

Go to Step 5

4 |

1. Turn ON the ignition, leaving the engine off.
2. Perform the scan tool clear DTC information function.
3. Operate the vehicle within Freeze Frame conditions as specified or until the P0132 diagnostic test has run. Refer to the Test Description.

Does the HO2S 1 voltage switch below and above the specified value?

300 mV - 600 mV

Go to Diagnostic Aids

Go to Step 5

5 |

1. Disconnect the HO2S 1 electrical connector.
2. Probe the harness side of the HO2S 1 ground circuit with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 7

6 | Observe the HO2S 1 parameter on the scan tool with the sensor electrical connector disconnected. Is the voltage less than the specified value? | 100 mV | Go to Step 9 | Go to Step 8
7 |

1. Check for an open in the HO2S 1 ground circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 11

Go to Step 10

8 |

1. Check the HO2S 1 signal circuit for a short to voltage.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 11

Go to Step 10

9 | Replace the HO2S 1. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | Go to Step 11 | --
10 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 11 | --
11 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to Diagnostic Trouble Code (DTC) List

System OK