I have an '04 XE KC. I have a simple aftermarket setup: Autotek Street Machine 200w 2-ch(older than the truck) to Infinity comps, Alpine 500w class d mono to 2 JL 10w0v3s. Kenwood hu almost as old as the truck. Suddenly the Autotek stopped powering on and the Alpine followed days later. Checked signal strength from proud and showed no voltage, so I replaced the hu. Still have the same prob. Checked voltage all around and found power to the amps drops to around 7 volts or less when the hu is putting out signal, but is still up to 13-14 when hu is on standby. Just don't know what would cause this or how it happened. Wiring, including grounds, all looks tight. Thanks for reading, all responses appreciated.
If one of your components has a bad power supply (bad transformer or power transistor(s)), when it powers up, it'll load down the system causing the source VDC to drop. Be careful because if it's hitting the entire system, it could fry your ECU.
pretty sure it is going to be a ground. Just because they are tight doesnt mean they are good. Pull them all make sure there is not rust. if there is rust or paint use a wire wheel to clean the surface, and then re tighten.
could also be corroded power cable. check around the under hood fuse and battery connection.
the only other thing I can think of that will cause voltage drop is a bad supply source, i.e. bad battery or alternator.