2000 kw t800 dash lights

I just upgraded and got myself a 2000 kenworth t800! My first week I ran it I had problems with my Trailer lights coming on and off randomly. I found out the fuse was slightly getting bent back and forth everytime I'd push the clutch in, and sometimes when I was going down the road would shake it just right to stop continuity. But this week I tried to start it up and none of my dash or gauge lights worked, everything else inside and outside does including map and dome lights. The gauge needles still work just the backlights won't turn on. Only thing I did was this weekend I swapped out oem radio for a JVC! I didn't know if the radio was messing with dimmer or if another fuse wasn't bad but just slightly getting bent again or bad fuse/relay! I read on another thread that if you don't turn your key to accessory long enough before cranking, it can mess with the computer or the dimmer switch or a relay and not let those lights come on! Didn't know if anyone's had something similar or knew where else I could start looking for the problem

 

It took a day but everything just decided to come on again‍♂️maybe loose ground or fuse

 

Does anyone know how/ if you can read engine codes from cab without engine code reader? My old mack you would just have to turn cruise off then hold Cruise set down and it would blink a sequence! Haven't needed it yet but wanting to know how / if for when it does it at 3am on a winter morning

 

I meant old as in previous truck.