2003 Tacoma 3.4 torque converter won't lock up in OD.

Just started having this issue. Trans shifts flawless otherwise. Did it to me yesterday morning, then after a little bit it decided to lock up. And worked fine after that. Did it again to me this morning, only it worked until I almost got to work then it didn't want to lock up again. Any ideas? I've searched threads but everything I can pull up is for a shudder and I don't have a shudder

 

It could be a fluid quantity and/or quality issue. You've checked both, right?

 

Yes full on fluid. Looks dirty so will change it out tomorrow. Are the filters on these just a screen? Was planning on using the flush machine at work to flush out my trans but wasn't sure if these had an actual filter.

 

Well I pulled codes for a brake switch, replaced and now torque converter locks and unlocks as it should

 

As a closure to this thread, I found that I had either a brake bulb that was shorted sending power back through my brake switch into my dash, or the brake switch itself was bad. I replaced all of the bulbs and switch and havnt had an issue since

 

Thanks for the follow up, this will no doubt help someone out in the future.

 

Good job !!!!
Its a computer controlled transmission and you followed proper procedure for the diagnostic by scanning for codes before guessing at the problem .
Here is some transmission information for you and I have more if needed
https://www.tacomaworld.com/threads...sions-write-up-your-4-speed-automatic.325531/