I confirmed today that my rear speaker is reading as an open circuit while my front speaker is about 50 ohms. Thank you again for the pictures and diagrams!
I plan to order a speaker and then dig into the headliner.
edit: I placed the order but I won’t be able to get to it for a few weeks as I am going on vacation.
Will be several weeks before I report back.
Here are drawings showing the BCM layout, reverse lamp signals and parking brake switch. The BCM layout shows the connector number e.g. C2280C and the pin numbers on each connector. Plug E is C2280E on the BCM. The reverse signal is a blu/wht wire, pin 20 on C2280E.
bcm layout.pdf
parking brake sw.pdf
reverse lamps.pdf