Dash lights up when I hit the breaks

[Kaibab]

Picked up a 2001 gen 3 a few months ago. While working my way through the typical issues such as blown out shocks, changing out fluids and a tune up I found a short. When I use the break pedal, the dash lights up like I had turned on the headlights. I pulled the dash and tried the ECU trick, but that did not fix the temp or fuel gages. I did find and replaced a missing ground strap from the transmission, but the short is persistent. Have any of you guys had this issue, or have a idea were to start checking?

 

[Pajero86]

Does it have trailer wiring? Mine did that when the trailer wiring adapter shorted out.

 

[Kaibab]

Looks like I will be under the truck tomorrow. Yes, it has an after market hitch and wiring harness for a trailer. Thanks for the idea.

 

[Kaibab]

Well tomorrow came a few days later than I had hoped. I pulled the aftermarket wiring off from were the former owner had scabbed it together and foud that he added a ground wire that was not really grounded. When ever I hit the breaks it must have fed back through the truck and been causing most (hopefully all) of my electronic issues. Now that it is back to the factory working, my dash lights don't light up, the fuel have and temp works and the check engine light turned off. Thank you Paj.