'99 Dodge Ram 2500 V8 AT, ~100K mi

My truck has randomly started stalling while driving.
No warning. Nothing consistent. Sometimes once a day, sometimes it'll go a week. Kinda dangerous as I loose all power steering/brakes etc. Hasn't happend at highway speeds yet but it has happened at random other speeds.
Sometimes it starts right up sometimes it takes 10-15min wait.
No codes thrown. I wish it did so I could start to track this down.

I recently noticed last time the LED Odometer displayed the 'NO BUS' when it died. Finally a clue

Searching here and around it seems this 'No Bus' is displayed when the PCM looses communication.

Seems this is not mechanical but electrical issue.

I see some state its a bad PCM or overheating PCM?
But there is no consistency with the heat.
On some hot afternoons I expect it to stall but it runs fine.

When I search for my PCM part number, 56040151AF I come up with nothing. This is the part # right off the sticker on the PCM, passager side engine bay. Why can't I find this part listed anywhere? I see other PCM's with the same 56040 but different last 3 digits?

I tried pulling the ECU plugs and blowing out, still no luck.
I tried pulling main plug on fuse box in engine bay, blowing out.
I tried the wire block driver side behind the e-brake looked for loose wires or loose bolt that holds the wire plug on.
Still it dies.

Suggestions? How do I further trouble shoot? I'm looking at putting a new/used/remanufactured PCM in, seems like a real easy job, but i am confused by my PCM part number I can't seem to find anywhere.

Help??

 

Probably not the PCM, more likely its either the cam, or crank sensor. They don't live in a very nice environment, and the symptoms you describe sounds like one or the other is failing due to heat soak. That's why it will sometimes take 10 to 15 minutes to start back up again. I would suggest crank sensor first.... get one from the dealer, our trucks REALLY dislike aftermarket sensors in critical areas.

 

Are you sure?

I mean the 'No Bus' that gets displayed on the Odometer is clearly a PCM communication failure, No?

Wouldn't a crank sensor or cam sensor throw a code? and not display 'No Bus'?

How would a cam or crank sensor cause a loss of communication with the PCM?

Also not sure of the heat soak thing, there have been hot days where I expect it die and it doesn't?

 

I too believe there is a strong possibility the crank sensor is failing. And no, neither one will always give a CEL.

 

Sure? Well, not 100% without actually being able to lay hands on the truck..... more like about 75-80%.....

One of the things that happens when the PCM loses crank signal, is after three seconds, it trips the ASD relay. I do believe that will give you a No Bus error on the dash. CMCKENNA had some REALLY good posts on troubleshooting no bus errors, might want to have a look at some of his posts, and see what ya find. He doesn't seem to have been around here for a while, but, His posts are still there.

 

Here's a good thread. https://dodgeforum.com/forum/2nd-gen...-bus-mean.html

 

I went through this already about six months ago, wasted time and money on a new PCM. Later to find out the "plug" on the PDC or main fuse block on the drivers side under the hood can collect moisture and corrode, Sometime causing the "NoBus" symptom. Thumb through these threads.https://dodgeforum.com/forum/2nd-gen...rror-code.html
https://dodgeforum.com/forum/2nd-gen...-no-start.html

 

Thanks for the links, big help. I couldn't find those with the search.

I have removed the plug on the main fuse box under the hood, blew it out and put a little elect. grease on the contacts and that didn't solve the issue.

I also did the same with the main at the driver kick panel behind the ebrake.

I need to look at crank and cam sensor.

I found a PCM for $250 from one of the big ECU places on so I am going to order that while I fiddle with the sensors.

 

Do the crank sensor first, and use a compressed air to blow out the hole like described in that one link.

 

Can someone point me in the right direction for?:

DIY- Cam sensor replacement
DIY- Crank sensor replacement

I did a search in the DIY section but nothing.

I downloaded the manual in that section but I couldn't find sensor replacement?