The present invention provides a system for automatically shutting down a vehicle. The system includes a vehicle system for performing a vehicle function such as brakes for performing braking of the vehicle. A vehicle control system controls the vehicle system by controlling valve switches or actuators to manipulate the vehicle system. A portable handheld computing device includes a program defining a vehicle shutdown sequence. Preferably, the portable handheld computing device is what is known as a personal digital assistant (PDA), such as a Handspring.RTM. or Palmpilot.RTM.. A cradle removably receives the portable handheld computing device to connect the portable handheld computing device with the vehicle control system, such as through the vehicle databus. A switch enables the portable handheld computing device to command the vehicle control system to perform the vehicle shutdown sequence. The switch may be an ignition switch, a dedicated vehicle shutdown sequence switch, or an icon on a PDA display touch screen. Once the switch has been actuated, the program residing on the portable handheld computing device commands the vehicle control systems to perform the vehicle shutdown sequence. For example, the vehicle shutdown sequence may command the pneumatic power control system to purge a wet tank to remove the water from the wet tank to prevent it from rusting.