Working on my 2001 Dodge Ram diesel. It first had a NO BUSS reading on the dash, and no gauges were working, but as i was driving it home, all the gauges came back, and the message went away. I took apart all the plugs, and they all look good. Checked the grounds and powers at the PCM and they are all good. I am using a snap on Brick scanner and i cannot access the body on system select. The trans and engine show no codes, they were probally cleared when the battery was unhooked, but the ABS and BRAKE lights are on. I checked the voltage on the ccd lines, and they are both 2.5 volts, which i believe is right. I also checked the CCD lines at the PCM and they are 2.5 volts as well. I did not remove the plug off the ECU to check it, i have not got there yet. I am leaning towards the possibility of a bad PCM. Any one have any ideas?

 

this is a fairly frequent problem that gets posted here, and one with no single, consistent solution. there are a lot threads here you can search. some people get fixed up by cleaning and retightening grounds on power steering bracket, or under dash driver side. some get fixed by finding blown fuses, especially IOD (i think). some unplug/replug pcm connectors. it could be pcm, but usually not.

ABS and brake is usually either tranny/t-case speed sensor or abs sensor on top of rear dif.

 

CCD should be 2.49 on one and 2.51 on the other. The voltage should fluctuate a bit too.If they are both 2.5 you have a problem.
Measure very carefully