Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Okay this is what I have going on. There is no communication to the pcm it starts up runs good. The transmission won’t shift and I can’t communicate to the pcm but that seems to be the only issues.
Here is a little back story.
it came in here for a head gasket probably 6 months ago. I had the head done and did the head gasket. They drive this truck as a hotshot service. Then They had a injector go out and wash out a cylinder. So he had someone else do the engine. They put it back together there selfs. And put a rebuilt transmission in it as well from jasper. They got it all together and it wouldn’t shift. Right off the bat I found the plug to the solenoids had a bent prong. The customer was still here so he took it and replaced the solenoid wiring harness that’s on the valve body. I didn’t even charge him diagnostics. Well then here it is back again same problem. After he changed it still no shift. I tried to communicate with pcm with no luck. I have checked powers grounds and bus. Everything looks fine. I took a pcm off my 2002 Dodge Ram 5.9L cummins to prove it is the pcm. My pcm will not communicate either so I put his on mine no communication. So I think they are wired differently when they went to common rail. They look the same but didn’t change out and work. So that leads me to have you ever had a bad pcm do everything but communication and shift? And am I right about the wiring in pcm?
Mine is a chevy but this may help. Exploring my ecu and the pins, I found that there were 3 pinout diagrams available for "mine" none of which matched exactly the reality of my ecu pins. I was looking for shorts to ground and ref signal goofiness in the O2 sensor circuits when i figured this out. Dealership was no help, as they used wiring diagrams from a**data which weren't accurate for my older 97 truck. You may have access to better data and be able to look inside your ecu harnesses to see if the pins to trans are same as old one. Could be as simple as one pin in the ecu harness got bent or they fried a fuse because of a mismatched pin. My chevy 2c...
Yeah I have looked and look and disconnected harnesses and check for omega. The pcm should communicate to the obd2 even without a transmission in it. So yeah I’m going to have to print out both pcm connecter plugs to see if they are different.
But I’m pretty sure it’s the pcm
The control of idle speed is a function of the PCM on all OBD2 equipped vehicles. The second method of communicating with the PCM is using an OBD2 diagnostic scan tool. The PCM's sensors and components interact with to control the various systems on OBD2 compliant vehicles.
Hey Mike did you get your problem with no communication to the pcm figured out?
I'm literally having the same problem after I got my transmission rebuilt. I've checked all the connection and ended up getting a new pcm but that didn't fix it so now I'm not sure what it could be.
Thanks
