I'm not an expert on late (post-75) models, but do have a few general
comments.

If you are getting a grinding noise from your brakes, it is probably because
your brake pads are down to the metal.

Brown smoke is undoubtedly electrical/electronic. Look for the source.

If you have ANY electrical nonfunction and you don't know exactly what it is,
the FIRST thing you do is make sure all the fuses are good and also that they
are making good contact.

If your engine runs OK, then the ECU is probably also OK.

If your buddy didn't know which way to hook up the battery, he is truly not
much help. Better off to do the work without him.

Put the Chilton book in file 13. Haynes and Bentley are better, Volvo is
best. As nearly as I can tell, the Chilton books are published to allow
management to check off a box on a form and to bring in money, NOT to help
someone who really needs to know how to fix his car.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma