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:
Cruise Control Light
The cruise control light is white whenever the cruise control is set, and turns
green when the cruise control is active.
The light turns off when the cruise control is turned off. See Cruise Cont ...
When the System Does Not Seem To Work Properly
If the LDW symbol does not appear:
○ The lane markings on the road may not be seen.
○ The camera sensor may be blocked by dirt, snow or ice.
○ The windshield may be damaged.
` ...
Taillamps, Turn Signal, Stoplamps, and Back-Up Lamps
To replace one of these bulbs:
1. Open the tailgate. See Tailgate on page 2‑10 for more information.
2. Remove the two rear lamp assembly screws near the tailgate latch strikerpost and pull ...