COSTAR-Tech Forum

2005 Corvette: found the OnStar module without any problems. Unplugged the 2 white connectors and plugged them into the CoStar unit. All worked first time. Volume adjustment appears to be through the radio. My only problem is space. The OnStar module takes up all the room behind the carpet, very little room for the CoStar. I unplugged the 2 black connectors on the OnStar mode to give me some additional cable to allow me to move the CoStar to the side of the OnStar unit. Once I did this the car wouldn't start. QUESTION: Does the OnStar module have the stay mounted and connected?

Yes, sometimes, GM uses modules to bridge the data bus. So when a module is disconnected, the data bus is broken.
In cases where there are wires in J4, you must leave them connected to the onstar module.