Hello, my name is Kevin,
I have been asked to help with your concern.
These vehicles had an issue with coolant or moisture getting into the bcm at the pass side floor board, causing the bcm & both dash units to fry. (all it takes is a drop) .
If you check the heater core box, I'll bet it is damp on the inside.
(look behind the glove box & you will see the programmer (has vacuum lines & elec. connectors) remove the programmer & the heater core cover).
If is damp, this is your cause. 7 times out of 10.
This is the best pic. I could find.
If it is not. then it is one of the three modules. Unfortunately there is no way to test the modules to find out which one ( or combo ) failed.
Be sure that the replacement modules part numbers match ( check your local bone yard & give them the part numbers off each piece ( on the back of each piece there is a part labile) to save yourself a trip)
replace the heater core if the box is damp, the bcm & both dash units no matter what.
be sure to use a gop of dielectric grease at the bcm.
If there are any further questions feel free to ask.
Best of luck,