Denali08

I am having similar issue with my 2003 Chevy truck.

The lights/sound alarm would go on for a second or two with all gauges droping off to zero left then go back to normal.

I already replaced the alternator with new OEM 145Amp and replaced my gauge cluster with new OEM but still problem did not go.

It happnes once in a while. I am suspecting the ignition start switch or the Body Module.

To OP, did u resolve the issue with your truck?

I done a check and here are DTC's history that I found using my HP Tuners scanner.

[Unknown] B2550 - Storage Mode Entered (History) (Current) (Immature)
[Unknown] B2575 - (History) (Immature)
[Unknown] B2580 - (History) (Immature)
[Unknown] B2600 - (History) (Immature)
[Unknown] B2610 - (History) (Immature)
[Unknown] B2961 - (History) (Immature)
[Unknown] U1000 - Class 2 Communication Malfunction (History) (Immature)
[Unknown] U1305 - Class 2 Data Link Low or High (History) (Immature)
[Unknown] U1016 - Loss of Class 2 Communication with VCM (History) (Immature)
[Unknown] U1160 - Loss of Communications with DDM (History) (Immature)
[Unknown] U1161 - Loss of PDM Serial Data (History) (Immature)
[Unknown] U1152 - Loss Of ACM Serial Data Communication (History) (Immature)
[Unknown] U1096 - Loss of Communications with IPC (History) (Immature)
[Restraints] U1041 - Loss of EBCM Communication (History) (Immature)
[Restraints] U1096 - Loss of Communications with IPC (History) (Immature)
[Restraints] U1000 - Class 2 Communication Malfunction (History) (Immature)
[Restraints] U1301 - Class 2 Short to Battery (History) (Immature)
[Restraints] U1016 - Loss of Class 2 Communication with VCM (History) (Current) (Immature)
[HUD] U1041 - Loss of EBCM Communication (History) (Immature)
[HUD] U1000 - Class 2 Communication Malfunction (History) (Immature)
[Entertainment] U1301 - Class 2 Short to Battery (History) (Immature)
[Entertainment] U1000 - Class 2 Communication Malfunction (History) (Immature)
[Entertainment] U1016 - Loss of Class 2 Communication with VCM (History) (Immature)
[HVAC] U1016 - Loss of Class 2 Communication with VCM (History) (Immature)
[Convenience] U1305 - Class 2 Data Link Low or High (History) (Immature)
[Convenience] U1016 - Loss of Class 2 Communication with VCM (History) (Immature)
[Convenience] U1000 - Class 2 Communication Malfunction (History) (Immature)
[Convenience] U1016 - Loss of Class 2 Communication with VCM (History) (Immature)
[Convenience] U1000 - Class 2 Communication Malfunction (History) (Immature)
[Convenience] U1305 - Class 2 Data Link Low or High (History) (Immature)

Denali08

Also, the rear view mirror that has compas and amp temp, stopped working for sometime. It worked again then went back to not working.

I mean the compas and temp readings in the mirror.

black00chev

iTrader: (2)

I have not gotten around to figuring it out. Haven't any problems with my mirror here. Im starting to think this could be partly from jumping a wrong wire for a split second once while diagnosing a bad switch a while back. Good chance its the BCM. I need to get a buddie to hook up a tech 2 and see what it can find out.

skolman91

iTrader: (28)

If you get time take off the the panel under the colum and check all the wires going to the bcm, anywhere they could rub or make contact or just make sure all the bcm stuff is snug and tight. My brother has i believe a 02 tahoe that had very similar stuff going on like it was losing communication while driving and from what im told was a bcm harness issue..
not much help..lol but just thought id mention it..

Denali08

Actually you got me closer. I will have to check those BCM wires.

Next is to replace the start switch.

Finally will be to replace the BCM and reprogram it.

Unless there is a way to check & test things before replacing.