GM Service Manual Online
For 1990-2009 cars only

Description

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the catalyst system. The test may be used to set the I/M System Status indicators to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing this test. Failure to meet the necessary requirements may produce inaccurate test results.

Conditions for Running

    • The barometric pressure (BARO) is more than 72 kPa.
    • Engine coolant is at operating temperature, 75-125°C (167-257°F).
    • The intake air temperature (IAT) is between -20 to +80°C (-4 to +176°F).
    • The engine is in Closed Loop fuel control.
    • The engine has run for 6-8 minutes off idle in order to initiate test.
    • The battery voltage is between 9-16 volts.

Diagnostic Aids

The control module runs a maximum of 6 tests per trip until the Catalyst System Status updates to YES. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

Test Description

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

  1. Perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.

  2. The Catalyst Test during the idle period immediately following the cruise period.

  3. This step is to identify a first failure of a type B DTC. A DTC only appears on the I/M System Status display when the DTC becomes a MIL illuminating DTC. This occurs on the second failure of a type B DTC. A first failure of a type B DTC will not allow the I/M System Status to update to YES. Refer to Diagnostic Aids.

  4. This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC.

  5. The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any Emission Related DTC sets after the tests are complete, the DTC will require diagnosis.

Step

Action

Value(s)

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 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 the specified time.
  4. Caution: Refer to Road Test Caution in the Preface section.

  5. Operate the vehicle within the following conditions:
  6. 4.1. Acceleration at part throttle to 89 km/h (55 mph) with this speed maintained for 5 minutes.
    4.2. Deceleration to 0 km/h (0 mph).
    4.3. The engine idling for 2 minutes while the following criteria is maintained:
       • The service brake is depressed.
       • The automatic transmission is in Drive.
       • The manual transmission is in Neutral with the clutch pedal depressed.
  7. Observe the I/M System Status display with a scan tool.

Did the Catalyst System Status update to YES?

2 Minutes

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 Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test.
  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 the procedure until the scan tool indicates the diagnostic test has run.
  7. Repeat steps 4-6 for any additional required DTCs that have not run.
  8. Observe the I/M System Status display with a scan tool.

Did the Catalyst 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