Is your scanner reading these codes from the DLC? Or is the whole network down? If your problem is in wiring somewhere then replacing modules isn't going to change anything. Was the 5 volt ref dead with all the PCMs you've had in there?
Hey I got a chance to work my my truck again 2007 trailblazer SS awd 6.0. I replaced fuse box. New ECM. TCM and bcm code u0100. My most problem is when I turn key to acc/run without starting my volt meter moves back and forth between 4v and 18v. I unplugged the pcm still does it. Pulled fuses still does it. Replaced cluster still does it and unhooked the splice connecter under the dash and only I connected wire to dash cluster still does it. (NEED HELP)😵 I isolated the circuit so it's from the battery to fuse box to cluster with nothing else on the network
I'm not entirely certain where the trouble may be. I do know the BCM sends battery/charging voltage readings to the cluster frequently during key ON and during engine on as well. Like as often as several times a second or as long as maybe 30 or 40 seconds apart, I suspect it is sent whenever there is a change. I believe this is where the cluster voltage reading comes from.
And where did you get the code U0100? From the PCM or BCM? That code is for a loss of communications. If there is trouble with the serial data communications,,, and the volts gauge uses the serial data,,, what you are seeing maybe a communications issue and not a battery issue??
I used a volt meter on my multimeter it Reed a solid 13.7 from the battery and steering column and from power wire that runs to bcm in rear. I just read the code from OBD2 don't know what circuit it came from.
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