Okay here goes, i have a 2002 escalade 6.0 ...
Its been sitting. in a body shop for about three months now. just got it back yesterday . (not sure if its relevant ). But my problem is that my radio has a mind of its own its an aftermarket clarion installed correctly an hasnt givin me any kind of problems till now.. When the truck is on the radio doesnt power up right away, usually after 15min drive the radio starts workin. also my onboard computer does not function. Like when truck is running its off but if key is on acc. position it works fine...but the radio never looses presets an still is gettin a constant power imo

Please help i really wanna enjoy my truck its been three months since i drove it!!

 

Have you tried disconnecting the Negative cable on the battery and leaving it off for like 10min?

 

If it was in for an insurance repair take it back. The body shop can get a supplement on the claim to get a dealer to check it out and get it working correctly provided it was that way pre collision.