Hi,

I don’t know anything about these cars but if it were mine I would dig up a wiring diagram from a good library data search or a shop manual.

From there you should be able to figure out how there’s power being distributed from a central point. At least a relay bank for the doors on older cars, before “CAN” WIRING BUSES. 2001 should not be a CAN.

The dealer should have access to things like that right away.
All kinds of service bulletins should have been issued over the years.
They may be in an archive but available for dealer requesting.
These are done easier by getting a “regional” customer service person in the loop. Not a service writer or manager of the local shop.
A decent dealer should have done this over the years for all those other customers of the past.
Especially if they want repeat customers.

As far as a battery leaking I could believe that it very possible over these many years.
If such a thing has happen inside a module, the circuit traces between the components, on the board, have been eaten into.
Just applying gunk to one incoming power trace would be plenty to kill the whole thing.
A repair would be to put in a jumper wire over the bad trace.

This is not the first time I have run into this.
My sister-in-law “had” a Range Rover with an inoperable sunroof that turned out to be a bad solder joint to a small module up behind the push button controller.
They wanted six hundred dollars to replace software for the brakes and install a new module for the sunroof. Of course after a diagnostics fee to confirm it was software.

I fixed the sunroof with solder and the brakes was a bad wheel sensor.
I cleaned all of them to conclude that it was one of three. The rear end was not it so get one sensor for the wheels and move it around. That was my diagnostics.

I said HAD above …
I saved her a bundle but when the special or exclusive made engine, from General Motors went bad, she junked it to charity. The whole vehicle of 2002 was also a nightmare of hodgepodge, with Lucas and Italian stuff inside.
If I remember correctly, Mercedes gave up trying to sort out the bugs within the company. Too British was the Germans excuse.
Or was that Chrysler and getting the Fiat 500 cars too?
Maybe both? Ford was jumping around with Lotus, Jaguars and Volvo.

You might still be lucky to fix things on this car yourself and learn stuff you’ll never forget.
Be a Scotty on your own ship and call it your private Enterprise. 🛠

Phil