So, I've been having a TCM communication fault for a long time now, you may have seen some of my other posts here, but I've come a bit closer to the cause recently, I think..
I plugged in the iCarsoft a few days ago and I noticed that the "errors" only increased when I put the car in or out of gear. It's like, the error coulter might be at 13 and when I shift from P to D it might jump to 17 and stay there until I shift back to P then it might quickly jump up to 22 or something.




This makes me think that it's either the rotation "dial" inside the TCM (in the image below) or the length of the shifter cable maybe being a bit off. My initial thought is that the conductors in the dial could be a bit worn, corroded, kind of like the way potentiometers go bad in radios and you get a scratchy sound as you adjust the volume. But I could be completely wrong and it could be something else.
This just seems like what the problem might be, with the way I get 3-4 quick errors when I move the gear lever. Maybe a bad seal on the TCM in this area and some moisture got in?




I did take the TCM apart a few months ago and everything looked fine inside, although I didn't take this dial part apart or anything.
Any other thoughts on what might be causing this TCM communication fault?
Would a badly adjusted cable give communication faults? Or what kind of symptoms would you see with this?
I think the fact that it only happens when I shift the lever narrows it down to this general area.
The car drives just fine. No limp mode, or jolts going into gear or anything like that.

 

Do not buy the Range Sensor.. Its a simple sensor and exorbitantly expensive. I had a similar problem,thought it was the Range sensor. Luckily I found one on E-Bay for $200 but, didn't solve the problem. Put in a new TCM that i bought used for $50 and everything was perfect.My TCM looked fine as well, but a coated circuit board would.

 

This is the TCM in these newer models with the 6-speed auto gearbox. It's a TCM and range sensor in the same box.