2000 dodge dakota 5.9l crank no start "no bus" displayed on the dash

hi everyone, this is my first post! fast background-i am a backyard type guy so no formal education on diagnostics beyond the scannerdanner vids and the book. yesterday my sons truck stalled while driving. we towed it home and after poking around i have this info.
no communication via my autel ms906bt or the bosch scanners i have.
no 5v ref-i unplugged the most easily accessible sensors (map, iat, iac, etc) with no change-still have o2, cam and crank to unplug and check to see if the 5v ref comes back or not. checked fuses and relays and all appears to be good (although i have not heard the fuel pump prime now that i think of it). this is a distributor engine and the ignition coil is not producing spark (test light method).
the pcm has good power and good grounds (ground wires are literally ground right next to the pcm). the pcm is easily accessible so we checked the 5v coming out and had .4v about 2" from the "A" connector. same result on the other 5v wire coming from the pcm as well. if we have a shorted sensor would it drag the 5v down at that connector? the pcm was very warm to the touch on the "A" connector side as compared to the other side of the pcm.
i do have the pico 4424 so decided to hook up the pico and the linespi to see if i could get can hi/lo signals just to see what happened. followed pico's directions (and double checked the set up as well) on how to hook it up and got garbage. by that i mean i got signals but did not look like the nice square waves they should look like but instead looked like spikes (sim looking to a o2 signal) and both channels pretty much matched each other. i have not got the hang of recording screenshots or waveforms yet so cant really post those up. consulting the great google seems to indicate that this no bus is a common issue with many different causes. any help/suggestions would be greatly appreciated. let me know if anyone needs further info to help point me and my son in the right direction. i am also using this to help teach both myself and my son.

i would definetly unplug the crank and cam sensors along with the o2 you havent unplugged yet. then if it still isnt 5 volts id unhook the pcm and do a short to ground test on the 5 volt ref circuit. should not see a connection from ground to that wiring.

Cheryl, thank you for the reply! will do what you suggest. question-could a grounded sensor cause a no communication with the pcm?

drawworkhome wrote: Cheryl, thank you for the reply! will do what you suggest. question-could a grounded sensor cause a no communication with the pcm?

Yes! I've seen it on with shorted cam sensors. Unplug the distributer and the the 5v ref comes back and the scanner will communicate again.
Check out this Scanner Danner video with a shorted VSS:

Noah-thank you! as soon as it stops raining here will give it a shot.

If unplugging all the sensors doesn't work, there is a pressure sensor inside the transmission that uses a 5v supply, I have seen the insulation on the wires that lead to the transmission short together due to being oil saturated. You can check this be unplugging the PCM connector C2.

rob, thank you.

And if you still haven't found it check the auto shutdown relay in the Underhood fuse box (also try banging on fuse box) I had 1 just last week with no start no com and no bus message that had a bad auto shutdown relay and something was going on in the fuse box intermittently I never did find what it was I opened the box up and couldn't find anything wrong so I cleaned it with electrical contact cleaner and compressed air and it hasn't acted up since so I assume it is fixed

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ben, i did check the asd relay and its working. my proof of that is the o2 heater fuse in the pdc gets its power from the asd and that is good to go along with the injectors getting their power from the asd as well. <edit>-i made the asd circut work with the uactivate tool. i am fairly certain the computer is not supplying the grounds tho) i am having an issue with the fuel pump relay in that i cannot hear the pump prime when the ignition is turned on. i do have power to the control and load sides like we are supposed to. my fuel pressure test kit is due to show up today so maybe i can see the fuel pump work then. i do have a uactivate tool that i used but did not do a current draw test yet-but will. my boy and i are using this as a learning experience so we removed the battery and took a look at the bottom of the pdc to see if there was anything obvious underneath and found nothing there. we decided to install new battery cables since the factory ones have seen better days so once that is done we can power things back up for further testing. the "new" computer shows up today so will see what happens. i am 99% certain the old computer died in the fact that the side of the computer closest to connector one was running around 125 degrees when powered up koeo and the other side was around (connector 3) was air temp roughly- along with no 5v ref from either 5v wire (one for engine the other for tranny all sensors unplugged) when tested right at the computer or anywhere else for that matter. all powers and grounds checked out as well. at least dodge put the computer in a easy to work on area.

for anyone interested in the solution for my vehicle-
a few months back the truck went to aamco to have the tranny rebuilt (overdrive grenaded). we found that when they reinstalled the tranny they crushed the crank sensor wires between the block and bell housing. must have taken this long to finally short it out. unplugged the sensor (not easy to get to at all) and 5v ref came right back and the no bus on the dash is gone. we had mistakenly replaced the pcm due to it getting really hot (i know....) on the c1 side but now knowing that the 5v is directly grounded i can just imagine the 5v regulator pumping out the juice at its max causing the heat. the original pcm is probably still good.
my son is getting a new sensor as we speak so fingers crossed all goes well later this afternoon. if anything new comes up i will post it up here.
i have to say without the vids of scannerdanner i never would have known what to do. thank you to everyone who responded to this post as well.

ended up being a shorted crank sensor between the bellhousing and block. i put a longer explanation as my last post.

Thank you for updating your post with the fix, it makes for a much better thread for everyone involved and also anyone researching a problem in the future.