GM Service Manual Online
For 1990-2009 cars only

Description

The purpose of this procedure is to satisfy the enable criteria necessary to execute an inspection/maintenance (I/M) system monitor for the system monitor for the heated oxygen sensor/oxygen sensor (HO2S/O2S) system. The system monitor is comprised of the test results from one or more DTCs. This procedure may be used to set the HO2S/O2S I/M System Status display on the scan tool to YES. The HO2S/O2S I/M System Status display indicates whether or not the control module has completed the system monitor. The system monitor completes when either all DTCs comprising the monitor run and pass, or any DTC comprising the monitor illuminates the malfunction indicator lamp (MIL). If one of the DTCs comprising the monitor is set and the MIL is not illuminated, the necessary trips are required to illuminate the MIL before the monitor will complete. Once the monitor completes, the HO2S/O2S I/M System Status display will be updated to YES.

Conditions for Running

    • The engine coolant temperature (ECT) is more than 75°C (167°F).
    • The battery voltage is between 10-18 volts.

Diagnostic Aids

If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load such as a cooling fan or A/C compressor clutch turning ON may cause the test to abort.

Step

Action

Yes

No

1

Did you perform the Inspection/Maintenance (I/M) System Check?

Go to Step 2

Go to Inspection/Maintenance (I/M) System Check

2

  1. Ensure that the vehicle is within the Conditions for Running specified in the supporting text.
  2. Turn OFF all of the accessories, e.g., A/C, blower fan, etc.
  3. Start the engine and allow the engine to idle for 2 minutes.
  4. Caution: Refer to Road Test Caution in the Preface section.

    Important: If the heated oxygen sensor/oxygen sensor (HO2S/O2S) I/M System Status updates top YES at any time during the drive procedure, proceed to the next step.

  5. Accelerate at part throttle to 75-90 km/h (45-55 mph) with this speed maintained for 18 minutes.
  6. Manual transmissions, either 5 or 6 speed, may require operation in 4th or 5th gear respectively, in order for this test to run.

  7. Review the I/M System Status display with a scan tool.

Did the HO2S/O2S System Status update to YES?

Go to Step 5

Go to Step 3

3

Observe the DTC Information with a scan tool.

Does the scan tool indicate any failed DTCs?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 4

4

  1. Refer to the Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to update the HO2S/O2S I/M System Status to YES.
  2. Observe the Not Ran Since Code Cleared display with a scan tool.
  3. Determine which of the DTCs required for a YES status has not run.
  4. Enter the DTC number in the Specific DTC menu of the scan tool.
  5. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC.
  6. Repeat numbers 4 and 5 of this step for any additional required DTCs that have not run.
  7. Observe the I/M System Status display with a scan tool.

Did the HO2S/O2S System Status update to YES?

Go to Step 5

Go to Diagnostic Aids

5

Observe the Emission Related DTC portion of the I/M System Status display with a scan tool.

Does the scan tool indicate any Emission Related DTCs set?

Go to Diagnostic Trouble Code (DTC) List

System OK