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 
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Advisor can run a check.
See also:
Headlamp Wiring
An electrical overload may cause the lamps to go on and off, or in some cases
to remain off. Have the headlamp wiring checked right away if the lamps go on and
off or remain off. ...
Convex Mirrors
WARNING
A convex mirror can make things, like other vehicles, look farther away than
they really are. If you cut too sharply into the right lane, you could hit a
vehicle on the right. Check the in ...
Back-Up Lamps
To replace this bulb:
1. Open the liftgate. See Liftgate for more information.
2. Remove the two screws from the taillamp assembly.
3. Pull the taillamp assembly rearward until the ...