General Description

The OnStar system consists of the following components:
^ Communication Interface Module (CIM)
^ Hand Free Microphone
^ Remote Control 3-Button Command Assembly
^ Global Positioning System Antenna (GPS)
^ Cellular Antenna

These components allow for wireless communications with the OnStar Call center, and cellular phone calls performed with hands free voice recognition.

The OnStar system is an integrated component in the vehicle, installed as a factory option. The Communication Interface Module (CIM) is interfaced directly with other modules on the class 2 bus, which allows for commanding outputs of other modules in addition limited remote diagnostics. The CIM is also interfaced via discrete wire to the radio allowing for sound from the OnStar system. The most interactive of the modules is the Body Control Module (BCM), where the OnStar CIM can perform functions such as unlock the doors, flash the DRLs with horn activation for tip to 48 hours after the vehicle is locked and ignition key removed.

The proper operation of OnStar is influenced by many factors outside of the vehicle. The System is dependent on cellular technology, Global Positioning System information, call center operation and vehicle component operation. Most of these systems are beyond the control and function of the limited on-board diagnostics. The importance of detailing the customers concern and checking with the support system to identify systems that were not functioning on the day of the failure will result in the proper diagnosis of the concern.