I have a 2000 Dodge Ram 1500 Sport. I am getting a no bus message and a check engine light. I have tried a code reader and it won't display anything. Truck runs fine but my instrument panel doesn't work. I did however notice the PCM was just dangling and not even attached by it's screws.

 

Remount the PCM, make sure it is grounded nicely. (I think there are even a couple wires for that purpose.) See if the no bus message goes away.

 

Even if the truck runs great and it's just my instrument cluster acting up? Also, there are no wires that I see. Can I just screw it on with regular screws? I don't want to short it out.

 

It kinda sorta grounds thru the case to the firewall, so yeah, whatever you got that will hold it in place will be fine.

Your truck has it's own little network. The PCM communicates with the cluster via the central timer module. As the truck runs good, the PCM is more than likely not the problem. Can check the connections at the PCM while you are remounting it, make sure they are clean, and tight.

If that looks good, need to dig a bit deeper. I *think* there are some troubleshooting steps in the 01 service manual, (same as your truck) you can download it from here.