Originally Posted by Oldblue

If you unplug the radio itself does the drain go away?

Originally Posted by firemangeorge

His bio shows the car is a 2008 model. Since that year had the known issue dealing with power loss affecting the programming , I would be careful about disconnecting any power wires while diagnosing.
Also which radio ? Regular or the upgraded one with the separate amp ?

Originally Posted by donbrew

What year is the car? Which radio?
Does the fob work as expected? Does the TPMS work? Is Onstar, XM/Sirius in the car, activated or not? Do you have the "Premium" radio with sub woofer and amp, steering wheel controls
Which fuse are you calling the "radio fuse"? Has ANY work been done before this started?

If the RAP relay was stuck you would be able to operate the windows when you first enter the car. If the RCDLR was involved the TPMS and fob would not work correctly, it is always hot on the same fuse as the radio.

What is the full code causing the CEL? One of them means "short to voltage".

The RDO fuse is always hot, the radio is turned on/off by a digital signal from the BCM, not the RAP relay.

Have you made sure that the dimmer wheel is not ON? Not all years have that.

Are all of the door switches operating correctly? Including the lift gate? Is there a fuse in position #11 under hood?