System Description

OnStar is connected to the vehicle, using the following components:





A Vehicle Communication Unit (VCU):

Primary component of the system. This unit is a 3-watt transceiver that connects the vehicle mounted OnStar system to the cellular carrier's communication system. It interprets commands from the VIU to initiate and end cellular calls to and from the OnStar Call Center. The VCU serves as a gateway between the VIU and the cellular carrier. The VCU can be identified by its The VCU can be identified by its small, flat, shiny metal case.





B Vehicle Interface Unit (VIU):

Contains the GPS receiver and the ability to exchange data with other Class 2 electronic modules or directly to specific systems. The VIU serves as the gateway for all messages between the VCU and the vehicle. The VIU is attached to a bracket located near the VCU and can be identified by its stamped sheet metal case.





C Cellular Antenna

Allows the VCU's cellular transceiver to transmit and receive radio signals within the cellular frequency range. The antenna must be correctly installed and extend above the roofline for proper operation.





D GIPS Antenna:

Allows the GPS receiver to receive signals from the orbiting GPS satellite network. These readings are then used by the VIU to determine the vehicle's position.





E OnStar Button Assembly:

- On* Button: Press this button to connect with an OnStar Advisor. You will hear a "chime followed by the words Connecting to On Star".

- Emergency button: In an emergency, press this button to connect to an OnStar advisor. You will hear a "chime" followed by the words Connecting to OnStar Emergency". The advisor will contact the nearest emergency services provider who can dispatch ambulance, police, fire or other emergency services to your location.

- Answer/End Button: Press this button to end a call. You'll hear the words, "OnStar request ended". Also, press this button to answer a call from the OnStar Center or to cancel a call if one of the other buttons is accidentally pressed.

- System Status Light:
Solid green indicates OnStar system in the vehicle is powered on and ready to make or receive calls.

Blinking green indicates there is a call in progress.

Red signals that OnStar may not be functioning property. Press the OnStar button to try to contact the OnStar Center. If your call goes through, OnStar will assist with any further steps to make sure the system functions properly.

NOTE:
Window tint with any metallic components will severely degrade antenna performance, resulting in customer complaints.





Symptom Table





System Check





DT # 1: OnStar Will Not Power Up - No Telltale/Red Telltale





DT # 2: Diagnostic Trouble Codes (DTC)





DT # 3: Button Assembly Test





DT # 4: No/Poor Cellular Connection





DT # 5: OnStar Commands Inoperative

NOTE:
Before proceeding, confirm horn honks with horn button and that hazard lights work with hazard switch. Repair circuits if necessary.





DT # 6: GPS Inoperative





DT # 7: No/Poor Microphone





DT # 8A: Radio Mutes But No Sound





DT # 8B: Radio Won't Mute





DT # 9: Power Consumption Test (Parasitic Draw)





Diagnostic Test # 10: DTC B0047 No Communication, OnStar to SRS