OnStar Description and Operation: Notes

1999 GMC Forward Control 5.7 R, AutomaticSECTION Notes
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The OnStar® system on this vehicle will be one of 2 systems, Generation 4 (Gen. 4) or Generation 5 (Gen. 5). Both systems are diagnosed identically, differing only in the audio prompt responses and output voltage to the microphone. To determine which system this vehicle is equipped with, install a scan tool and access the Module I.D. Information screen. The Gen. 4 and Gen. 5 versions of OnStar® both consist of the following components:

  • Vehicle communication interface module (VCIM)
  • OnStar® button assembly
  • Microphone
  • Cellular antenna
  • Navigation antenna

This system also interfaces with the factory installed vehicle audio system.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.