My gut says, and its not always right, that someone maybe messed with the CJB (central junction box) which is on the passenger side behind the glove boxes. The rear connectors can be a HUGE pain to get right. So if someone was back there and messed with it, a connector may not be seated well. Heck, I swear I had mine seated well and they were not. Such a tight space. Sometimes taking the bolts out that secure it in the location can help.

 

Interesting thought. So you are saying there may be a loose wire behind the Fuse 'Panel behind the Glove box (or CJB I guess it is). I need to look at the manual
and see what ABS or TCM wires are ran into that panel versus under the hood. Once I get the new Terrain Control and Parking Brake switches in today or tomorrow I will
install... crank and reset the codes... I will report back on what is popping up. Thanks for the recommendation.

 

Not a wire, but a connector on the backside. There are connectors both front and back. I dont recall how many on the backside, I think three maybe? And the CJB is also the fuse panel. Its one complete unit and specific to the truck, can not be easily swapped with another. I think it requires reprograming. It could even be water damage. Since your passenger side was dry, it *might* be possible that there was a water entry issue with the sunroof drain and it was repaired. But corrosion took over. Either way, its something to at least rule out. Im just surprised with the issues you have you are not getting more specific codes.

 

OK... I got the replacement Terrain Control Switches and Parking Brake Switches. No difference. Cleared all codes... and let it run for a few minutes... All codes came right back almost immediatly

U0121 and U0122 pop up under several systems (Engine, Transmission, ABS, etc)

U0121 Lost Communication with ABS Module (From what have read this could be causing all the other faults). Could this be ABs Sensor at 1 of the wheels? However, I am not getting a wheel speed sensor fault code.
U0122 Lost Communication with Vehicle Dynamic Control Module (No idea here... also heard this could be cause of all faults)
PO504 Brake Switch A/B Correlation Error (I've already changed the Brake Switch... so no idea why this code came back)
U0416 Invalid Data From Vehicle Dynamic Control Module (Linked to U0122 I am thinking)
B1B52 Rear Sounder error (reverse system failure... seems this 1 is common and probably not serious)
B1B02 Low frequency coil - General signal failure (I think related to the ignition circuit but not serious

Oddly enough... The U0416 and U0122 show up in the Automatic Gearbox ECM and cause the dash diagnostic to show a Transmission failure message.

Not sure where to go from here.... I wanted to see a bad AB sensor but all I see is the U0121... so what could that be? Maybe wiring at CJB?

What ya think guys?