I have a 2000 1500 with the 5.9 magnum engine and got the no bus in the odometer truck won’t start. Plugged scan tool in to check for codes and the truck starts and runs fine with the scan tool plugged in,but if you unplug the scan tool the engine dies and back to no start.

 

Oh, now that one is going to be FUN to figure out..... Given it starts and runs with the scanner plugged in, I would suspect a fault in the communications bus somewhere. Trouble is, it's EVERYWHERE...... Usually, it's some sensor on the five volt feed that cause those types of problems, (no bus) but, since yours starts with a scanner plugged in.... all bets are off.

 

I got 'no bus' on my '01 5.9 a few yrs. ago; turned out to be one of the terminals at PCM. Reseated all 3, started up fine.

First check the grounding strap on the PCM to the firewall for a tight connection, no rusty surfaces. Then unplug the three terminals by pushing down the release tab and pulling evenly on left & right side of each, not on the wires but the rectangular plastic. Check for loose or bent pins, look at the holes in the terminals for gunk, loose wires at terminal, & maybe use an old toothbrush to brush the pins on the PCM and their terminals, then plug them back in. I didn't disconnect my battery but you might want to just for safe measure. Reconnect it after reconnecting the PCM.

Good luck!

 

interesting my truck is missing that ground strap

 

Same here.

 

You probably have another one somewhere else. There should be a small wire to the negative cable from the fender or radiator support. Those tend to corrode and the firewall strap is to supplement it in case it fails. Really heavy duty electrical systems have grounds all over the place to reduce radio noise. My last P71 Crown Vic had straps on the firewall (2), hood, trunk lid, exhaust and transmission housing. There may have been more I never noticed.

 

I do not have one. I am missing a few though. I wonder if they'd why my passenger speaker makes a high pitch noise when the radio is off

 

I do. I have one at the firewall (I noticed that it was broken and fixed it while replacing the crank sensor a few months ago and there is another near the front of the driver's side fender). I think there may be others. I did install another one between the truck bed and the truck frame when I swapped out my rotten 8 foot bed with a pristine used one a few years ago..

 

Most of the time, extra grounds don't hurt but can help. There is one caveat though. If you need to do some welding on the vehicle, make ABSOLUTELY POSITIVELY sure you disconnect BOTH battery cables from the battery. An arc from welding can back flash through acid build up on the battery casing. This will play hob with computerized systems on the vehicle. A couple of years after I had a factory engineer tell me this, I watched an alternator start to smoke while the frame was welded.

I also clean the battery cases once a year on my cars now too.