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:

    Starting the Vehicle Messages
    FAST IDLE ON If your vehicle has this feature, this message displays when the fast idle feature is on. See Fast Idle System on page 9‑31 for more information. ...

    When to Check and Change Automatic Transmission Fluid
    A good time to check the automatic transmission fluid level is when the engine oil is changed. Change the fluid and filter at the intervals listed in Maintenance Schedule on page 11‑3 and be su ...

    Tire Designations
    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 ...