Onstar

Is it?

Yes but not enough to cause a battery problem. Once the battery is charged after starting, the alternator provides the power to your accessories (radio, blower, engine, etc.). Have the "tone" looked into if you cannot turn it off. I assume it happens only when the car is running. If not, it will eventually drain the battery but it will take a few days at least.

Thanks for reply. Looking now into disconnecting the Onstar unit itself, looks like a real bear. Descriptions to do so, access from trunk do not match my car. access to power box by backseat removal may be my best option, nothing simple