Description
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the evaporative emission (EVAP) system. The test may be used to set the I/M System Status indicators to YES. Service Bay Tests are included on the scan tool for some systems depending upon vehicle make and model. The test is designed to allow the EVAP diagnostic tests to run in service bay conditions. Ensure the vehicle meets the requirements listed in Conditions for Running before performing either EVAP System Test. Failure to meet the necessary requirements may produce inaccurate test results.
Conditions for Running
Scan Tool Service Bay Test Equipped Vehicles
| • | The barometric pressure is more than 65 kPa. |
| • | The engine coolant temperature (ECT) is less than 70°C (158°F). |
| • | The fuel level is between ¼ and ¾. |
| • | The battery voltage is between 10.0-18.0 volts. |
Diagnostic Aids
Extreme high or low ambient temperatures may prevent the EVAP System Tests from initiating. Performing a visual inspection prior to running the EVAP Service Bay Test may prevent having to repeat the test. A loose fuel cap may cause a Service Bay Test to abort or fail and prevent the I/M System Status from updating. A failed or aborted test will require the vehicle to cool down in order to meet the enable criteria to run another test.
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 updates to YES. If a test for a specific system has failed, the I/M System Status updates 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 indicates 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 cool down.
The I/M System Status updates only when the DTC fails the second time, or 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 A/C compressor clutch turning ON may cause the test to abort.
If a diagnostic test is difficult to run, observe the I/M System Status display while maintaining the necessary enable conditions until the system status updates to YES.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
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This step is to determine whether or not the EVAP System Test has passed. If the system is operating correctly, the scan tool indicates that the system has passed and the I/M System Status updates to YES. If the EVAP Service Bay Test aborts because of lost enable conditions, the test can be repeated once the enable criteria is met.
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A failed DTC during the EVAP Service Bay Test may not appear in the DTC Information display on some vehicles. The Service Bay Test displays an indication of which test failed as a directive to the appropriate service information. Some vehicles will display the test as aborted and the first failure of type B DTC appears in the DTC Information.
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The EVAP System Test usually begins around an engine coolant temperature of 80°C (176°F). The vehicle should be operated moderately until this temperature is reached. The engine coolant temperature can be monitored using the scan tool.
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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 it 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.
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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.
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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 | Yes | No | ||||
|---|---|---|---|---|---|---|---|
Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | ||||||
2 |
Is the vehicle equipped with EVAP Service Bay Test? | Go to Step 3 | Go to Step 5 | ||||
Did the EVAP system pass the Service Bay Test? | Go to Step 8 | Go to Step 4 | |||||
Is the repair complete? | Go to Inspection/Maintenance (I/M) Complete System Set Procedure | -- | |||||
Important: Once the engine is started, DO NOT turn the engine OFF for the remainder of the procedure until the test is complete. 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: After the specified time has elapsed, Chevrolet Metro, Prizm, Tracker and Cadillac Catera vehicles require the following additional steps:
Did the EVAP System Status update to YES? | Go to Step 8 | Go to Step 6 | |||||
With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? | Go to Step 7 | ||||||
Did the EVAP System Status update to YES? | Go to Step 8 | Go to Diagnostic Aids | |||||
With a scan tool, observe the Emission Related DTC portion of the I/M System Status display. Does the scan tool indicate any Emission Related DTCs set? | System OK |
