GMC Repair: Fuse Box problem, rain sensors, fuse block

Question
Dear Jim,
The question(s) I have might be aided by the fuse blocks pictures (which I think you can access at https://www.mygmlink.com/pdf/go2content/manual/US/en/gmc/2002envoy.pdf). I have a 2002 GMC Envoy and some of the electrical is not working now that I accidentally connected the jumper cables to the wires going into the engine compartment fuse block (power surge), and may have even connected + to -, and vice versa. I have both an engine compartment fuse block and a rear underseat fuse box.

I pulled each of the fuses on both blocks and none of them appear to be broken. Pete told me to unplug the negative for 5 minutes to try to reset the computer, but that unfortunately did not fix it. I did some more hands-on research on exactly what features aren't working on the SUV. ALL of the features to which the engine compartment fuse block fuses run work fine (the block is page 6-58 of the user manual at the link I put above). In addition 4 to 7 of the applications/functions which are run by fuses from the rear underseat fuse block work (page 6-61). These are all in a cluster (Cruise Control, Frt Wpr, Lt Turn, Rt Turn, and probably the Ignition 0, Rain sensors, and the "Truck Body Controller Ignition" fuses). However, every other feature controlled by the rear fuses does not work--i.e. heat ventiliation air, radio, rear fog & parking lamps, all door control modules [including power doors, windows, mirrors, and security system/remote entry], and interior lighting.

I suppose I have 3 questions which any help would be SO much appreciated:

1) Are there any common denominators (i.e. relays, master fuses, etc.) that could be shot or need resetting? I'm hoping its NOT the body control module, and I think it might not be, since some of the rear fuse block's functions work.

2) What can I do, short of taking it in, to attempt to find and fix what's wrong?
and
3) Where is the truck body control module located?

I have access to a high school autoshop which has some testing tools, etc.

Thanks!


Answer
O.k. I am going to just start from the beginning.

First the I/P BATT fuse is the fuse that powers the rear fuse block, it is in the underhood block(UBEC). This fuse controls the power to all of the disabled systems that you have mentioned.

Second you should check that fuse, and if it is good check for power coming into the rear fuse panel at the bid red wire, and out of the UBEC, at a terminal on the side of the UBEC. Also check for continuity since you may have fried the buss bar.

Third the Truck Body Control Module is attached to the rear fuse block.