dash cluster is all screwed up with lights flashing & buzzers sounding. My 2004 chev silverado has only 32,000 miles
You may be looking at a bad BCM.
might have a class 2 serial data problem . . .
Are the gauges showing incorrect information? Like low fuel or no oil pressure? Almost all of these trucks needed to have the instrument cluster rebuilt or replaced for erratic gauge operation caused by the stepper motors going bad.
Another thing that could be causing this problem is high ripple voltage coming from the alternator. To see if that is the case simply disconnect the connector on the back side of the alternator and start the engine. This will disable the alternator output and will make the dash work like it should if the trouble is with the alternator. If it is bad it is due to bad diodes inside it.