Hyundai Repair: Code P0740, torque converter clutch, transmission control module tcm

Question
The check engine light in my 20020 Santa Fe 3.5l AWD started coming on intermittently about a week ago, had the code read by my local mech. He got P 1529 and P0740, had to go to the dealership though to find out what they mean.  Apparently there's an issue with a Torque converter valve.  Per dealer, looks to be about $320 for the labor to pull apart the transmission, then $52 a pop for the part.  Also advises that there are five valves involved in the torque converter, and do I just want to replace the one that's thrown the code, or all five since they will already be in there.  What's your take on all this, or do you need more info?

Thanks!

Answer
P0740 indicates a torque converter clutch issue, and P1529 indicates a request by the transmission control module (TCM) for the engine control module (ECM) to illuminate the check engine lamp.

If the problem is indeed in the solenoid, then I'd recommend just replacing the one solenoid.  These solenoids don't fail very often, so the chances of having an issue with another in a short period of time are low.

My concern, however, is that the solenoid may not be the issue.  It's possible that you have a valve body issue, an internal transmission seal issue, or an issue with the torque converter itself.  Unfortunately, you'll probably need to replace the solenoid to find out whether that's the issue.  If the solenoid doesn't repair the issue, Hyundai's recommendation is to replace the transmission.

I recommend that you read technical service bulletin (TSB)05-40-006-2.  Hopefully, it'll help you understand what I'm talking about.  You can see Hyundai's TSBs at www.hmaservice.com.  You'll need to register for a free account, and the site requires Internet Explorer.