Vehicle: 2002 dodge ram van 2500 5.2L

About three months ago I was driving the van and it started not accelerating when the pedal was pushed down further than an inch it would stall out and come back upon release and a couple seconds. I took it to a machanic and it was reading codes for an o2 sensor and the cam shaft sensor. During this time it was having a hard time starting. The engin would turn over but just not fire. I had both of those replaced along with the ignition coil. The van ran great until a week or two ago when I turned it off in the rain and it wouldnt turn on again. It was doing the same thing turning over but not firing. Upon opening the hood I noticed smoke coming from the ecu. I had it towed to the machanic. I bout a rebuilt ecu and it was installed a few days ago. Now the van still won't start and is running a camshaft sensor code again. Is it possible that the camshaft shorted and caused the ecu to short or the reverse chain of events. They are going to try replacing the new camshaft sensor again. But what could be done to prevent this happening in a month again. What could be the problem.

 

Since this happened after raining...
1. Are you sure it was smoke and not steam coming from the ECU?
2. Did you remove the distributor cap and check for moisture under it?

 

I'm pretty sure it was smoke as it would only happen when I was tryin to start the van. And once the ecu was removed smelling it smells like burnt plastic. As for moisture under the distributer I'm not actually doing the repair it's at a shop they just cannot figure it out so I was seeking advice.

 

Is it possible that the only ecu was starting to go and shorted the cam shaft sensor, and then when it finally broke it shorted it again. Would replacing the camshaft and the van running mean the problems solved or could something still be wrong