Multiple TCM Codes

So, I have a transmission problem and my truck is throwing 22 TCM codes, I will give a quick jest of the problem.

So, the problem started out about 8 months ago - wouldn't lock into fifth gear and when mashed on the pedal the passing gear (dropping down to pass) wasn't happening, slow and sluggish.

Following that 1 month later after 30 minutes of driving the truck would just shift into only third -fourth gear and wouldn't come out of 3-4 gear unless it was put back into neutral or park and reverse. Then you could start to drive it again and in a matter of minutes, back to only 3rd and 4th gear.

Fast forward, it sat all winter, because I don't have a garage to get it into.

This Month (May), now that the weather is tolerable - dropped the trans pan - no debris (or material)- fluid is a beautiful red - replaced all the solenoids with OEM and wire harness, but during the investigations under a plate (Trim solenoids) there are two springs, one was broken into three pieces. Replaced both of those springs as well as the Psm and the MLPS switch on the outside of the transmission, plus a new wire harness (found mine was leaking trans fluid during the inspections).

So, none of this stuff was replaced by me or anyone else since I had purchased the truck 8 years ago, so I figured now was the time to do it since I'm dropping everything down.

(Replaced all filters as well for transmission)

Well that fixed nothing.

First it was shift inhibited when I finished up, so
I replaced that electronic lock in the steering column (no change).
checked all the fuses, (they are good).
Fluid is full.
Checked the pins on the TCM (seated tight).
relearned Transmission.

I reset the main TCM harness and cleaned it up, and the Shift inhibited went away, I was able to drive the truck and it was moving, like I haven't felt in a while, had power, nice shifting, everything was great in the 20 minutes I drove it.

Wife jumped in it and drove another 20 minutes and it went out of gear and then automatically locked into fourth.

She would put it into park, reverse works as it should, put it into first, and within 3 seconds would lock into fourth. You hear the transmission, just change gears at a standstill to the fourth. Messed around with it a bit more, cleared the codes, shifted through all the gears, but after a few seconds, automatically into fourth and locks. Run diagnostics and found 22 Errors.

It's sounding like a communication problem, but I am not sure. I keep thinking the TCM is messing up judging by the codes she is throwing at me. But again I am unsure.

Anytime you start it up throw it into reverse - no shifting issue - neutral - no problem put it into Drive and she will sit in first gear for 5 seconds then you hear it shift into fourth and lock, just sitting there idling not driving with your foot on the brake.


I am not asking you all for a miracle but some trouble shooting steps to start following, I am asking with everything that I described, does it sound like the TCM is stepping out on me and needs to be replaced? As Much as I want to purchase and slap a TCM I don't have a lot of money to just parts change to hope for a fix.

Mike L from DuramaxDiesels. Com said this : The problem is you through every code in the book. Every gear is slipping, you have speed sensor codes, you have tie up codes (2 gears at once.) You have valve body codes. Start with a known good TCM and see what codes come back. Then move on to the valve body.


So, I am asking for your guy's opinion if buying your TCM is the way to go with this?

Thank you much. Mike