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:
Active Fuel Management®
Vehicles with V8 engines may have Active Fuel Management™. This system allows
the engine to operate on either all or half of its cylinders, depending on the driving
conditions. When less power is ...
Torque Lock
(Automatic Transmission)
Torque lock is when the weight
of the vehicle puts too much
force on the parking pawl in the
transmission. This happens when
parking on a hill and shifting the
transmission into P (Park) is ...
Footnotes — Maintenance
Schedule Additional Required
Services — Normal
a) Vehicles with different size front
and rear tires do not have tire
rotation. See Tire Rotation.
b) Or every two years, whichever
comes first. More frequent
replacement may be needed if the ...