Got new tires and now I have a shift solenoid problem
 

I recently just purchased new Michelin tires for my rear. They're the size they're supposed to be with the only difference is them being zr rated (my transmission is automatic and everythingis stock besides new valve spring/ titanium retainers). All of a sudden after driving away I get the abs and traction lights along with the ol' P0700 and P2757 codes coming up followed by a little jolt once it dropped from 2nd to 1st. I don't understand how a tire change affected that besides maybe the tcm was used to my almost bald tires and out of nowhere new tires. I tried with my toyota dealer since I've been already trying to get them to flash my ecu due to the infamous idle drop since it correlates with the tcm but for whatever reason no recall on their end comes up with my vin despite it being a 2015 fr-s but they don't want to "risk" flashing it. I'm also aware of the TSB but alas no help.

I literally just rebuilt my engine after it being down for 2 years and it ran perfectly fine for the last 4 months til I got new tires. I was wondering if anyone had insight on the situation.

Anything helps, Thank you.


Update 4/14/23: I cleared the check engine codes but it still left the permanent codes on. Let the car sit for the night and everything just went away. The car shifts fine if not better now and doesn't jolt from downshifting 2nd to 1st. I also somehow got my notorious rpm idle drop to go away.

(Theory): since the TCM does in fact communicate with the ECU in regards to gas distribution. I think what may have happened is that since the new tires gained traction a lot faster than almost bald tires the tcm was confused as to why it doesn't take more power to speed up therefor throwing a code for the torque converter being stuck because it wasn't requiring more gas/torque to move. Weird how that happened but I'm glad it didn't end up being more serious.

Nothing to do with the new tires. The only thing the TCM see's in regards to the tires is wheel speed. Those are both TCM com issues with the transmission from what I can tell. There are a few threads on it.

https://www.ft86club.com/forums/showthread.php?t=144469

change the front tires to the same tires as well and the problem will go away.

blame subaru's stringent awd-programmed ABS system

New tires are 5/8" larger in diameter than bald tires, +2.5%, not insignificant... Are the fronts nearly bald?

Reading comprehension fail on my part. Did not notice he only replaced the rears. I would think this would trigger TCS to act funny, kinda how a poor alignment will, and not codes for communication issue with the transmission control.

No my front tires are perfectly fine, it was just my rear that was almost bald.

Exactly, I wasn't too surprised over my TCS and Abs to do something funny but my shift solenoid saying it's having issues shifting out of nowhere the moment the TCS and Abs go up doesn't make sense to me. Literally everything was fine before I got my tires replaced.