EVAP Service Bay Test

Diagnostic Instructions

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 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:

EVAP Service Bay Test Status — Running

The vehicle must remain at rest, in Park, or in Neutral, during this portion of the test. This test inspects for large leaks and vent system restrictions. The purge valve leak diagnostic may run, but is not required. The scan tool will display test progress or the reason for an abort or failure.

EVAP Service Bay Test Status — Vehicle Ready for Drive Cycle

The scan tool will display time and distance needed to warm the fuel. The drive distance remaining rounds down to zero when there is anything less than 1 mile or kilometer remaining. The vehicle must be driven until the “return to service bay” message is displayed.

EVAP Service Bay Test Status — Engine Off Conditions Met

During this portion of the test, the ECM will remain active for up to 45 min when the ignition is turned OFF to allow control of the EVAP vent solenoid valve and run the engine off natural vacuum test. The ECM 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 not within the calibrated values indicate a leak.

Note:

  • Do not reorder the scan tool screen display. The EVAP Service Bay Test Status parameter is the main status message to observe. It will indicate when each category is active with the Test Results status parameter right beneath it.
  • There are many possible screen messages. It is very important that you watch these messages and record any failure or abort message as this will aid the diagnosis.
  • If any of these issues occur during or after the engine running portion of the test, the vehicle will need to soak for at least 8 h before retrying.
  • An incorrect “drive distance not met” message is an indication that the service bay test aborted earlier and the vehicle was keyed off followed by retrying without waiting for at least 10 min before retrying.

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 completed or failed.

If

  • The Service Bay Test aborts
  • The scan tool resets
  • The scan tool locks up
  • The scan tool sets an error
  • The diagnostic connector becomes disconnected

    Before starting the engine, the vehicle should be left keyed off for at least 10 min before retrying.

After the ignition off portion of the test has completed, the Service Bay Test will delay ECM shut down for 10 min to allow for analysis of scan tool data. A complete Test Results status message along with EVAP Monitor Complete value of YES is the goal.

Conditions for Running the Test

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

  • The battery voltage is between 11–32 V.
  • The engine coolant temperature (ECT) is less than 35°C (95°F) at start-up.
  • The intake air temperature (IAT) is less than 34°C (93°F) at start-up.
  • The ambient air temperature is between 0–40°C (32–104°F) at start-up.
  • The fuel level is within 10–90% capacity and cannot be refueled during the tests.
  • The vehicle must have sat for 8 h since the last run time.
  • The EVAP I/M System Status indicator is set to NO.

    • Note: The use of the scan tool Clear DTCs function will reset all I/M statuses.

  • There are no DTCs displayed.
  • The vehicle must be driven for the time and distance specified on the scan tool.
  • The ignition must remain OFF during the engine OFF portion of the test, and the vehicle must remain at rest.

Test Procedure

Note:

  • If the Service Bay Test aborts or fails, a DTC will NOT be set.
  • You must not rush the scan tool selections or erroneous results or error messages could occur.

  1. Select the Service Bay Test with the scan tool.

    2. Warning: Refer to Road Test Warning.

  2. Follow the instructions on the scan tool. The EVAP Service Bay Test should complete and should not abort or fail.
    • If the test aborts

      Correct the condition for running the test, then retest.

      or

    • If the test fails

      Repair the vehicle for the condition indicated by the failure message, then retest.

    • If the test passes

      • Note: There are several test parameters displayed and can vary by engine RPO.

  3. Verify that the EVAP Monitor Complete parameter, is set to YES.