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 
, and an Advisor can run a check.
See also:
Roadside Assistance Program
U.S.: 1-888-881-3302
TTY Users (U.S.): 1-888-889-2438
Canada: 1-800-268-6800
Mexico: 01-800-466-0801
As the owner of a new GMC, you are automatically enrolled in the Roadside Assistance program.
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Instantaneous Economy and Active Fuel Management™ Indicator
If the vehicle has this display, press the trip/fuel button until INST ECON V8 displays. This display shows the current fuel economy at a particular moment and will change frequently as driving condit ...
Brakes
Brakes stop the vehicle and are crucial to safe driving.
• Signs of brake wear may include chirping, grinding, or squealing noises, or difficulty stopping.
• Trained dealer technicians have acce ...