GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

If the PCM detects that the HO2S 1 voltage is above a calibrated amount for an excessive amount of time, DTC P0132 will set.

Each HO2S 1 has the following circuits:

    • An HO2S 1 high signal circuit
    • An HO2S 1 low signal circuit
    • An HO2S 1 heater ignition voltage circuit
    • An HO2S 1 heater low control circuit

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1

Conditions for Running the DTC

    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, where applicable, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0442, P0443, P0446, P0449, P0455, P0496 are not set.
    • DTC P2A01, P0401, and P0420 are not commanding fuel.
    • The system voltage is between 9-18 volts.
    • The scan tool special functions are not active.
    • The following conditions must also be met:
       - The TP sensor parameter is between 3-40 percent.
       - The Air Fuel Ratio parameter is between 12:1 and 16.5:1.

Conditions for Setting the DTC

    • The HO2S 1 voltage is more than 889 mV for 100 out of 125 samples for at least 6 sets of samples. Each sample is 100 ms.
    • The PCM detects that the HO2S 1 signal voltage is more than 889 mV for more than 75 seconds.
    • This diagnostic runs continuously.

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.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Start the engine.
  2. Allow the engine to idle at operating temperature. Refer to Scan Tool Data List .
  3. Clear the DTC and record the Freeze/Frame Failure Records.
  4. Observe the HO2S 1 parameter with a scan tool.

Is the voltage more than the specified value?

889 mV

Go to Step 4

Go to Step 3

3

  1. Observe the Freeze Frame/Failure Records 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/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4

  1. Turn OFF the ignition.
  2. Disconnect the heated oxygen sensor (HO2S) 1 connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the HO2S 1 parameter with a scan tool.

Is the voltage more than the specified value?

889 mV

Go to Step 6

Go to Step 5

5

Is the voltage less than the specified value?

15 mV

Go to Step 7

Go to Step 8

6

Important: The HO2S 1 may have been damaged when the HO2S 1 high signal circuit was shorted to voltage. Verify proper operation of the HO2S 1 after completing the repair.

Test the HO2S 1 high signal circuit for a short to voltage. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

7

Test the HO2S 1 high signal circuit for a short to the HO2S 1 heater low control circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

8

  1. Turn OFF the ignition.
  2. Probe the HO2S 1 low signal circuit, on the engine harness side, with a test lamp that is connected to B+. Refer to Probing Electrical Connectors .

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 9

9

Test the HO2S low reference circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

10

Inspect for the following conditions that may affect the HO2S operation:

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

    • HO2S contamination--Inspect the HO2S for contamination.

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

    • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring
    • An open or high resistance in the HO2S 1 low signal circuit
    • Evaporative emission (EVAP) system malfunction--Inspect the EVAP control system. Refer to Inspection/Maintenance Evaporative Emission System Set .
    • The fuel pressure--Incorrect fuel pressure can affect HO2S operation. Refer to Fuel System Diagnosis .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

11

Test for an intermittent and for a poor connection at the harness connector of the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

12

Test for shorted terminals and poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

13

Replace the HO2S 1. Refer to Heated Oxygen Sensor 1 Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

15

  1. Clear the 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.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 16

16

Observe the Capture Info with a scan tool.

Are there any DTCs that have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK