I have a 2006 cadillac cts base model, bose stereo system. Did the parasitic draw down test and isolated the draw to problem. Installed an amp,no help. Installed a radio,factory radio no longer available, bought from eBay. Did not have the radio matched to my vehicle. Same situation, no help. Pulled fuses to both,radio and amp and battery was fine. Battery check,fine. 3 month old battery. Tried disconnecting the antenna module, no change. I don't have a programmer to start replacing models. At $150 from the dealer each time would cost more than the vehicle is worth. I don't mind paying for a bcm or ecm but if one doesn't fix the problem I'd have to purchase the other,have it programed on and on. Any assistance in this situation without an expensive programmer like a tech 2? Thank you for your assistance
This is going to be rough without a scanner. The 1st thing you may want to consider is putting back the original radio and the original amp since changing them out didn't fix the problem.
The reason I say that is because these are modules on a serial network and sometimes we can create another problem that's unrelated to the original problem when we swap parts and that can leave you "chasing your tail".
The radio and amp used to get power through the RAP (Retained Accessory Power) relay in the older GMs and that's what I expected to see for yours but yours doesn't work that way.
You still have a RAP relay but the radio and amp aren't powered through it.
Your radio and onstar module (if you have that) and your amp have direct power from the amp fuse and the audio fuse.
I looked up some Cadillac CTS wiring diagrams and even though this one doesn't show everything in the radio/amp circuit it's good enough for discussion. It's the same generation CTS as yours.
I highlighted Red for Power and Purple for the Serial communication network from the BCM.
You can see that your AMP always has power (B+ in the upper left of the diagram) and the audio fuse that powers your radio and onstar also always has power (because it's fed by the AMP fuse).
The radio and amp are turned on and off by signals over the BCM's serial network.
I looked at your owners manual regarding the RAP function. Here's a screenshot:
But I'm not sure I agree with all of it. The Power Windows and the Sunroof are powered through the RAP relay. The radio and amp aren't.
I think the RAP relay stuff will "timeout" after 10 minutes but i think the radio and amp are allowed to function until the BCM gets a signal to terminate RAP mode and passes it on to the radio/amp.
One of the ways the BCM communicates with the radio and amp over the serial network is by signaling if the ignition key is in the ON position or if the BCM is commanding RAP Mode.
Like the owners manual description says, one thing that will terminate RAP is if the BCM gets a signal that the drivers door has opened after the key is switched to the OFF position.
So the "low hanging fruit" here are the ignition switch and the drivers side door ajar switch.
If you have the onstar module it could be shorting out and scrambling the network signal but you can just unplug it to rule that out.
Ideally you'd hook up a bidirectional scanner and go into the BCM and command the RAP mode On and Off to confirm that the BCM is able to control it to rule out a problem with the BCM. That would narrow it down to the RAP termination inputs.
Anyway, that's just my 2 cents but you're dealing with a complicated system with the BCM, a serial data bus, modules, and inputs from other sensors/switches and their wiring. The problem could be in any of those.
@jack62 should be able to help with this. My understanding is that the radio and amp are supposed to be on switched ignition circuit while a small amount of full time current is used from another circuit to maintain radio settings and the time.
