GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The heated oxygen sensor (HO2S) heater is a device used to reduce the time that the HO2S takes to go active. The powertrain control module (PCM) controls the HO2S heaters using low side (ODM) drivers. The PCM uses a current monitoring driver to test the condition of the fuel control heaters. A high side driver provides HO2S bank 1 sensor 1 heater with ignition voltage. A low side driver provides the ground path for both of the heaters. With the engine running, the PCM turns ON the high side, and the low side driver to warm-up the oxygen sensors. If the PCM detects an incorrect circuit condition for the commanded state of the current monitoring driver, this diagnostic trouble code (DTC) will set.

Conditions for Running the DTC

    • The system voltage is between 9-18 volts.
    • The ignition is ON.

Conditions for Setting the DTC

The PCM detects an incorrect circuit condition for the commanded state of the current monitor driver.

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

If the condition is intermittent, refer to Intermittent Conditions .

Step

Action

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. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, clear the DTCs.
  3. Turn OFF the ignition and wait 30 seconds.
  4. Turn ON the ignition with the engine OFF.
  5. With a scan tool, monitor the DTC information for 30  seconds.

Do DTCs P0030, P1031, and P1032 set?

Go to DTC P0030

Go to Step 3

3

  1. Start the engine.
  2. With a scan tool, monitor the DTC information for 30 seconds.

Do DTCs P1031 and P1032 set?

Go to Step 4

Go to Intermittent Conditions

4

  1. Turn OFF the ignition.
  2. Disconnect the HO2S bank 1 sensor 1 harness connector. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 .
  3. Turn ON the ignition, with the engine OFF.
  4. With a test lamp connected to B+, probe the HO2S bank 1 sensor 1 heater low control circuit.
  5. With a scan tool, command the HO2S heater driver 3 ON and OFF.

Does the test lamp turn ON and OFF?

Go to Step 9

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

  3. Disconnect the HO2S bank 2 sensor 1 harness connector. Refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 .
  4. Turn ON the ignition, with the engine OFF.
  5. With a test lamp connected to B+, probe the HO2S bank 1 sensor 1 heater low control circuit.
  6. With a scan tool, command the HO2S heater driver 3 ON and OFF.

Does the test lamp turn ON and OFF.

Go to Step 8

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Disconnect the PCM connectors. Refer to Powertrain Control Module Replacement .
  3. Test the HO2S bank 1 sensor 1 heater low control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

7

Test the HO2S bank 2 sensor 1 heater low control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Replace HO2S bank 2 sensor 1. Refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 .

Did you complete the replacement?

Go to Step 11

--

9

Replace HO2S bank 1 sensor 1. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 .

Did you complete the replacement?

Go to Step 11

--

10

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 11

--

11

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

Does the DTC run and pass?

Go to Step 12

Go to Step 2

12

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