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:
Bulb Replacement
For the proper type of replacement bulbs, see Replacement Bulbs.
For any bulb changing procedure not listed in this section, contact your
dealer. ...
Tire Pressure for High-Speed Operation
WARNING
Driving at high speeds, 160 km/h (100 mph) or higher, puts an additional strain
on tires.
Sustained high-speed driving causes excessive heat buildup and can cause sudden
tire failure.
Yo ...
Safety System Check
Now and then, check that the safety belt reminder light, safety belts, buckles,
latch plates, retractors, and anchorages are all working properly. Look for any
other loose or damaged safety belt s ...