I've had multiple transmission problems and a runability issues with my truck. As of late. I've replaced sensors, the PCM and never really got any codes. I had another post going and a lot of help from the forum trying to suss out what I thought was a misfire which after going through everything suggested was narrowed down to my torque converter locking and unlocking with light throttle input. Fast forward to two nights ago I break down on the side of the road. The truck starts right up and shuts right down. I noticed that my scanner will only communicate with the engine portion of the PCM when the truck is running. Not simply with the ignition switch on. This has been happening intermittently since this transmission shop did some really **** work to my truck. I have a feeling all of the issues are related! ! So my question is what would cause the scanner to communicate with the PCM only when the truck is running but it can communicate with every other system without the engine running?

 

That's an odd one.... The comm bus is active whether the engine is running, or not.... Does the volt gauge indicate anything with ignition on, engine off? Or does the needle just sit on its bottom stop?

 

Voltage needle moves with ignition on then goes past the halfway mark when the truck is running

 

So it may just be a problem with the diagnostic port, and not the bus itself.

 

I don't believe so because the unit powers up and comunicates with all other systems minus the engine

 

Ok, now, that's just weird...... I really don't think that is 'normal' behavior..... but, WHY it would work that way???? Something isn't powered when the engine is not running? Makes me wonder just what the trans guys did to your truck.....

 

Exactly what the fk did he do

 

sorry I had to buy another vehicle and sideline truck . here's where I am at . I was spraying some brake parts cleaner around the intake manifold looking for a leak when it burst into flames ! luckily my buddy who works for dodge was present and was quick to point out that would only happen due to an electrical short . that makes sense considering the truck inter intently shutting down , misfiring and not throwing a single code ! problem is short of removing the entire Ain engine wiring harness I don't see anything obvious ! so I'm hoping to gain some input to further narrow down what I should be looking for ? I was considering just replacing the entire main and manifold harnesses but would much rather repair it since I do pretty good wiring work and no matter what I find the harness will be old and most likely need repairs so might as well re[pair the one I have but again don't see any obvious bad insulation or compromised wires . any help would be greatly appreciated !

 

Either a wire is getting hot enough to ignite stuff, (which I would think would also cause other damage..... which would be obvious...) Or maybe a plug wire leaking? Do you actually HAVE plug wires on that? That's the only thing I can think of that carries enough current to actually arc.

 

No plug wires they are coil packs of the penciled variety. I've sprayed plenty of brake parts cleaner around intake manifolds never once had it burst into flames never mind engine was cold