instrument panel cluster issues

[Leviticus Stuart]

So I recently took my truck to the shop for the Instrument Panel CLuster as all the gauges would either be frozen or not turn on when i started the vehicle. Shop could not duplicate problem, suggested replace ipc. IPC replaced and as soon as I'm driving it home it starts having another issue. Now it is as though the IPC keeps resetting itself while I'm driving as if i had turned the key back to ACC and all my warning lights come on, gauges reset. The shop had it for an entire month while i was gone at work and could not find the problem. They still have not given me a list of what they tested. But it was at least the trailer brake module and the stereo. The guy who was doing the work is on vacation I should be getting a write up soon. I checked the problematic vehicle grounds on the frame cleaned and shined them up it did not help. I have installed a new headlight dimmer switch that did not help. Moved the aftermarket fuel pump to a new fuse that did not help. Disconnected the aftermarket marker lights. Did not help. Nothing has helped. I do not know what to try and now the shop wants even more money to fix something they didn't fix in the first place. Any ideas where to start?

 

Also this is problem occurs much more frequently on the initial start up in the morning. Once the vehicle is warm or it is warm outside the problem is not as persistent.

 

Also while the shop had it they were probe testing the IPC and did have a loss of communication to a module. Module unknown. I have asked about replacing the IPC and he doesn't want to to do that yet because if they send it back and it isn't bad then he is on the hook for a whole IPC. 

 

There was a code for the front end impact sensor which i replaced. Sometimes the IPC will go out then turn back on and the airbag light will stay on. Other times it will not turn on. And also every time i restart the truck the airbag light is off. So I don't think that is the major cause. 

 

Vehicle is a 2008 GMC sierra, extended cab, SLT, Duramax, 4x4. 2500HD. 

 

I replaced all the glow plugs as well. I have not fixed the lumbar support code yet but i did disconnect the lumbar support switch and problem still persisted. 

 

Seat heaters have not yet been replaced either.

 

Only thing i could think of is maybe an ignition switch failure? Shop did say they tested that and it was ok. 

 

This a  reputable shop around town. I do not think they are trying to screw me at all, its a very professional and the owner is extremely polite and I have been dealing with him directly. I am mechanically inclined but not so electrically inclined which is why i took the vehicle in. I have a pretty good sense for when somebody is ****ing me over.

 

Thanks to all those who respond anything helps.