00 Silverado Interior Lights Not Working

[toy4x4]

2000 Silverado Regular Cab

 

My interior lights don't work when I open the door, use the dimmer switch or press the buttons for the two overhead lights. The Cargo light also does not work as I assume this is part of the "interior lighting".

 

The strange part is the little status display always reads "Cargo Light On" even though it is not.

 

I was able to get rid of the message by disconnecting a harness. This harness is the one that goes into a box that is mounted to the firewall just to the left of the brake pedal. I removed the black cover over the box and it has three relays in the front and two harness connecting on the front. One is a two wire harness with two black/white striped wires and this does nothing, but the larger harness with 8 or more wires if disconnected at least gets rid of the "cargo light on" message.

 

Any ideas what could be causing the interior lights not to work while causing the "Cargo Light On" message to always display?

 

Also, what is the box with all the wires going into it(most in back) mounted on the firewall just to the left of the brake pedal?

[toy4x4]

Spent the $20 for the Chilton online manual for my truck.

 

The second wiring diagram I printed out showed the CSTY fuse was in the interior light circuit. Bam, it was blown. Fixed.

 

Looking at the fuses earlier I would have never guessed CTSY stood for Courtesy.

 

Thanks Chilton!

 

(still confused on the cargo light message staying on... but really don't care anymore)