The Service Bay Tests are included on the scan tool for some systems depending upon vehicle make and model. The service bay tests initiate the operation of certain PCM controlled functions, assisting the technician in system diagnosis.

The EVAP purge/seal function is designed to seal the EVAP system with a vacuum applied. The test allows the technician to monitor the fuel tank pressure (FTP) sensor , for any vacuum decay. The purge/seal function can also alert the technician of an inoperable purge, vent, or pressure switching solenoid. When the EVAP purge/seal function is enabled, the PCM commands the vent and pressure switching solenoids ON or closed. The purge solenoid is commanded ON, open, allowing a vacuum to enter the EVAP system. After 30 seconds the PCM commands the purge solenoid OFF, closed, sealing the system. The EVAP system will remain sealed for 150 seconds. The FTP sensor reading should be approximately -23.45 mm Hg (-12.50 in H2O).

In order to perform the EVAP purge/seal test with the scan tool follow the procedures below:

Important: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. Fuel tank pressure may increase on a hot vehicle due to the thermal expansion of vapors in the fuel tank.

Important: Fuel tank fill levels can affect the results of the diagnostic procedure. Fuel tank pressure may increase on a warm vehicle that has less than one third a tank of fuel.

1. Run the engine to normal operating conditions.
2. Install the scan tool.
3. Turn ON the ignition, with the engine OFF.
4. Remove the fuel fill cap. The FTP sensor should read near 0.0 mm Hg (0.0 in H20).
5. Install the fuel fill cap and start the engine.
6. Enable the EVAP purge/seal function on the scan tool.
7. The FTP sensor reading should decrease to a -23.45 mm Hg (-12.50 in H2O), indicating a vacuum has entered the system.
8. Observe the FTP sensor reading for 2 minutes. If there is no evidence of vacuum decay, the FTP sensor reading should remain at -23.45 mm Hg (-12.50 in H2O).

Check Mode can be used to increase the ability of the powertrain control module (PCM) to detect engine control system malfunctions. The PCM can be requested to operate in Check Mode by using the Output Controls feature of the scan tool. While in Check Mode operation the PCM will turn ON the malfunction indicator lamp (MIL) and record Freeze Frame data even on the first failure of a B type DTC. Not all engine control system diagnostics will be enhanced by Check Mode operation. The Check Mode service bay test can be performed while driving the vehicle in order to duplicate the customer concern. Those diagnostics most commonly known to benefit from Check Mode operation will be specified in the diagnostic procedure.

In order to activate the enhanced diagnostics of Check Mode operation, perform the following procedure:

Important: DO NOT turn OFF the ignition anytime during or after the operation of the vehicle in Check Mode. Observe and capture all Check Mode operation DTC and Freeze Frame information on the scan tool before turning OFF the ignition. Any DTC or Freeze Frame information that occurred during Check Mode operation will be cleared by the PCM when the ignition is turned OFF.

1. Capture or save any DTC or Freeze Frame information on the scan tool before entering Check Mode operation. All DTC and Freeze Frame information will be cleared by the PCM when Check Mode is entered.
2. Turn ON the ignition, with the engine OFF.
3. Enter Check Mode operation with the scan tool from the Special Functions selection. Verify that the MIL is flashing which indicates that the Check mode request was received and accepted.
4. Return to the Data List selection on the scan tool.
5. DO NOT turn OFF the ignition after requesting Check Mode operation with a scan tool. The PCM will return to Normal Mode operation when the ignition is cycled from ON to OFF to ON.
6. Start the engine.
7. Operate the vehicle within the conditions under which the original concern was noted or within the Freeze Frame conditions that set the DTC.
8. The Diagnostic Mode parameter in the scan tool data list can be viewed at anytime in order to verify that the vehicle is still operating in Check Mode.
9. If the MIL illuminates while in Check Mode, observe and capture all DTC and Freeze Frame information with the scan tool.
10. Check Mode operation can be terminated by cycling the ignition switch, or commanding Normal Mode with the scan tool.