System Operation (Release System Diagnosis)

PARKING BRAKE RELEASE SYSTEM DIAGNOSIS

The climate control system uses vacuum to change air flow positions. A quick test to check for proper vacuum is to select different air modes. If the air flow direction changes from defroster vent to I/P vents to floor vents then the vacuum source is operating properly. If the Heater and A/C Programmer is not receiving the Class 2 (Serial Data) request from the PCM then a loss of serial data Diagnostic Trouble Code (DTC) will be set by either the Heater and A/C Programmer (132016), PCM (P1605) or both. The Scan Tool provides a test for exercising the Park Brake Release Solenoid. If the status of the Park Brake changes with the Scan Tool, and Park Brake does not release, check for proper vacuum supply at the solenoid. If there is no vacuum at the solenoid, inspect the vacuum hose and hose connector and repair the vacuum supply as necessary. If the vacuum supply is OK, replace the solenoid. However, if the status does not change with the Scan Tool, this indicates that the Heater and A/C Programmer is not responding to the request of the Scan Tool. Inspect terminal connections and if OK, replace the Heater and A/C Programmer.