GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2005 🢒 Ascender - 4WD 🢒 Engine 🢒 Engine Controls - 4.2L 🢒 Inspection/Maintenance (I/M) Catalyst System Set Procedure

Description

The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the catalyst system. The test may be used to set the I/M System Status indicators to YES.

Conditions for Running
    • The barometric pressure (BARO) is more than 74 kPa.
    • The engine coolant is at operating temperature, 71-120°C (160-248°F).
    • The intake air temperature (IAT) is between -15 to +75°C (+5 to +167°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 11-18 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.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the malfunction indicator lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs).

The first failure of a type B DTC does not constitute a final determination of pass or fail, and will not update the I/M System Status to YES. A second trip is required, and all the conditions to run must be met in order for the test to run again. These conditions may include a partial to complete engine cool down.

The I/M System Status will update only when an emission related DTC fails the second time, or when all of the tests pass.

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 an A/C compressor clutch turning ON, may cause the test to abort.

If a diagnostic test is difficult to run, maintain necessary enable conditions until the system status updates to YES.

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 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.

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

    Important:  In order for this test to run, the vehicle must operate in the following conditions:

  4. Acceleration at part throttle to 90 km/h (56 mph) with this speed maintained for 5 minutes.
  5. Deceleration to 0 km/h (0 mph).
  6. Engine idling for 2 minutes while the following criteria is maintained:
    7. • Service brake depressed
    • Automatic transmission in Drive
    • Manual transmission 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?

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 - Vehicle

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 - Vehicle

System OK