Diagnostics

OnStar Vehicle Diagnostics will perform a vehicle check every month. It will check the engine, transmission, antilock brakes, and major vehicle systems. It also checks the tire pressures, if the vehicle is equipped with the Tire Pressure Monitoring System.

If a diagnostics check is needed between e-mails, push OnStar Additional Information, and an Advisor can run a check.

    See also:

    Tire Size
    The following is an example of a typical passenger vehicle tire size. (A) Passenger (P&-Metric) Tire: The United States version of a metric tire sizing system. The letter P as the first chara ...

    Charging System Light
    The charging system light comes on briefly when the ignition is turned on, but the engine is not running, as a check to show the light is working. It should go out when the engine is started. If t ...

    Blizzard Conditions
    Being stuck in snow can be a serious situation. Stay with the vehicle unless there is help nearby. If possible, use the Roadside Assistance Program (U.S. and Canada) on page 13‑8 or Roadside As ...