2001 Ram 1500 No Bus 920 921 999 Dash Code

I have an 01 Dodge Ram 1500. I was driving it to work one day when it completely shut down all of a sudden while driving. A "no bus" code on the dash popped up, and when I tried to start it again, it would crank but not start and I had to get it towed back to my house. I've been messing with it for a few weeks now and noticed it starts occasionally and if I do get it to start it shuts itself off again and still reads "no bus". I used my OBD2 scanner and get no communication to the ABS everytime whether I get it to start or not. I just replaced my ABS module with a used one I got online and I still have the same outcome as I did before. I replaced my battery as well (not that it would fix it, but it needed a new battery anyway).

I did the instrument cluster test and codes 920, 921, and 999 popped up on my dash. I've done some research and i'm almost positive that its a bad pcm or theres a bad connection going to the pcm. Whats the best way I can test the pcm without just guessing and buying a new one? Please tell me what you guys think.

I am unfortunately having the same issue.

Did you figure it out?

"nobus" means that the gauge cluster has lost communication with the computer. The gauges all move and do their thing based upon inputs from the computer, so no comms means they all just flatline and a handy "nobus" appears in place of the odometer to inform you of this.

I had this problem a few years back, but the engine still ran just fine. Turned out to be a faulty timer module for the windshield wipers. Yeah, all of the truck's electrical systems are kinda sorta connected via a main bus line (I think the whole works is referred to as "Chrysler Collision Detection"). It's basically a multiplexing system that allows all electronics to be fed from said bus line, or something like that. I'm gonna shut up now, because I'm now in danger of painting myself as someone who actually knows how it all works (I really don't).

Basically, a glitch in just one of those modules can apparently prevent the gauge cluster's intended received signals to not reach the cluster, hence my old problem.

ANYWAY, the problem you seem to be having is that not only is the gauge cluster not receiving any inputs from the computer, but the computer itself is either malfunctioning, and thereby preventing the engine from running, or you've got a wiring problem, which is also preventing the engine from running. The former can be resolved by simply replacing the computer, or, if you're feeling intrepid, you can yank it apart and try to find/replace the faulty component (I'm pretty sure there was someone here who actually succeeded in doing that a while back). If it's the latter...no comment.