2016 TRD Weird Transmission (?) Issue

I'm a 2nd gen owner but my nephew has a 3rd gen. He recently got rear ended. He's not sure if it's coincidence but after that his truck starting acting funny. When he's at a lower speed it feels like he's tapping the brake. His truck kind of stutters. At higher speeds the issue is gone. When he turns on ECT the problem goes away. When it starts to stutter, he gets a CEL but it goes away quickly. When it stutters he can turn off his truck and restarts it goes away for a little while but it comes back eventually. For now driving around with ECT is what he's doing and it's fine.

He's going to pull the codes to see if that tells him anything. The accident was just a minor bump. No major damage. It's an automatic.

Any ideas what it might be?

 

On rear exhaust cars I always suspect exhaust damage, but tacoma is out the side. Is there any chance it was hit?

Need to scan the code for sure and document it.

 

He's going to do that tomorrow I believe. I'll post back when he does.

 

Could be a torque converter issue. Sometimes, even when functioning properly, the converter locks up on downshifts and gives the sensation of braking that maybe perceived as a "stutter" at times. ECT will lock the converter essentially eliminating the automatic lock up function so it wouldn't happen in that case.

Codes will be interesting to see and truly the only way to get started with finding the issue.