Is there a Brake Pedal sensor?

Hello, you're correct, there is a brake pedal sensor, it's a 6-wire sensor on the brake pedal that sends a signal to the Body Control Module and to the Transmission Shift Lever, as well as the engine computer (ECM). It's possible that the Brake Pedal sensor needs to be recalibrated. Or the Transmission Shift Lever needs to be reprogrammed. They are on the BUS network, and all communicate with each other. The fact that you're having to press the brake pedal many times to get modules to shut down and go to sleep indicates an issue in that area. I'll put the wiring diagrams below so you can get a sense of what the circuits look like, but the brake pedal basically 2 sensors in 1. Half goes to the Body Control Module and half to the ECM. Doing a brake pedal relearn procedure may take care of the issue. Also doing a full system scan may come up with codes stored in other modules than just the ECM. Most basic scan tools only scan the engine computer, so a code might not show up if an auto parts store does a code scan on the vehicle. You can try that, but it may not pinpoint the issue. Check the s brake pedal sensor connector too, being that its down by your feet, it's in a good location to get corrosion or dirt in the connector.
I've also put the calibration procedure below, but you'll need a scan tool capable of doing that relearn.
There is actually a Technical Service Bulletin on this, I will post shortly.
Pages 5-10 below are a TSB on an issue with the parking pawl, which is the component that holds the transmission from moving while in Park. If there's any other information I'll post it here.