Please help, I got on here trying to help my brother in-law with his 2000 Ram 1500 5.9L sport 4x4, any time after he drives in the rain his truck will not start, but, when you turn the key you can hear the starter relay click but nothing else happens. it is throwing a no bus code, also, when he turns the lights on his cluster lights dont work unless he clicks on his high beams. we have disconnected the battery over night to see if anything changes but nothing did. There is one random ground wire thats not connected to anything and from what ive seen there should be a ground wire on the computer thats under the hood but that was on a van not sure if being a truck would make a difference but i think its worth noting.

 

Ground wire wouldn't cause that. A no bus message means a sensor on the 5v system is bad or a bad wire. The light issue is most likely a ground issue. Need to do a lot more testing.

 

Yeah and CCD Bus work is more advanced than basic electrical trouble shooting.

Fanatic is right about a 5v sensor. I'd start troubleshooting the CKP (crank position sensor) which would cause a no start. The 5V reference is shorting to ground or the data output is shorted to 5V or ground. I'd look more at the wiring and connector than the sensor itself due to the rain issue. I doubt the sensor could be cracked and letting in water. Use plenty of dielectric grease in the connector after cleaning it up. Check wiring back to the PCM.

Could try wrapping the PCM and harness near it in plastic to see if there's no issue in the next rain, then you know where to look or not look.

I'd also check where the harness goes into the cab to the cluster, maybe wire insulation has been rubbing against the opening where a grommet has been knocked loose (possibly when wiring an amp and using the same opening in the firewall). There is one place on driver side below brake booster, looks like a big rubber plug in the firewall, someone could have punched it loose to feed in more wire, and now unprotected wires have been rubbing against the opening... wild guess.

 

The OP stated the truck is a no-crank but the starter relay is clicking. The cranking circuit is fully "analog" on these old trucks, just switches (ignition, neutral safety/clutch interlock) and relays with no PCM control like in newer vehicles. I'd start with the basics of solid power and ground connections to the starter, from the engine block etc.. E.g. the PCM is grounded at the front of the engine block but if the block itself doesn't have a good connection to battery negative the PCM won't run.

 

Thank you everyone for your input for what to check, but, y'all ain't gonna believe this!!! This whole time it was a dang 20amp ignition fuse 🤣🤣🤣🤣🤣