For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Description

The purpose of the evaporative emission (EVAP) Service Bay Test is to aid in resetting the EVAP inspection/maintenance (I/M) system status. For this vehicle that is equipped with the engine off natural vacuum (EONV) diagnostic, the Service Bay Test uses the scan tool to initiate the engine control module (ECM) regular sequence of EVAP system DTC tests, but with different enable criteria. By using the Service Bay Test the I/M indicator can be set without the need for multiple cold soaks.

The scan tool displays for the Service Bay Test are based on the events that occur within the following three categories:

• | The engine running portion of the tests--The vehicle must remain at rest, in Park, or in Neutral, during this portion of the test. This test inspects for large leaks, a leaking purge valve and/or vent system restrictions. The scan tool will display test progress or the reason for an abort or failure.

• | Drive cycle--The scan tool will display time and distance needed to warm the fuel.

• | Ignition OFF--During this portion of the test, the engine controller will remain active for up to 45 minutes when the ignition is turned OFF to allow control of the EVAP vent valve and run the EONV test. The engine controller inspects for small leaks during this period by monitoring fuel tank pressure or vacuum. If the system is sealed, there will be a pressure or vacuum change. Pressure or vacuum changes that are less than the calibrated values indicate a leak.

When the EVAP diagnostics are initiated by the Service Bay Test, the scan tool will indicate if the enable conditions listed below are not met, or will display a specific reason if the test aborts. When complete, the display will indicate that the tests passed or failed.

### Conditions for Running the Test

The following conditions must be met in order to enable the Service Bay Test:

• | The battery voltage is between 11-18 volts.

• | The engine coolant temperature (ECT) is less than 70°C (158°F) at start-up.

• | The EVAP I/M system status indicator is set to NO.

• | The fuel level is 15-85 percent capacity and cannot be refueled during the tests.

• | There are no DTCs displayed.

• | The vehicle must be driven for the time and distance specified on the scan tool.

• | The ambient air temperature is between 0-40°C (32-104°F).

• | The ignition must remain OFF during the engine OFF portion of the test, and the vehicle must remain at rest.

### Test Procedure

Important: If the Service Bay Test aborts or fails a DTC will NOT be set.

1. Install a scan tool.
2. Select the Service Bay Test with the scan tool.

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

3. Follow the instructions on the scan tool.

⇒ | If the test aborts, correct the condition for running the test and then retest.

⇒ | If the test fails, repair the vehicle for the condition indicated by the failure message on the scan tool.

4. Verify that the EVAP I/M system status is set to YES.