Hyundai Repair: Transmission Control Switch, transmission control module, hyundai sonata

Question
We have a 2001 Hyundai Sonata GLS. We will be driving along and all of the sudden the engine jerks and the car switches to a lower gear. The only way to get it to stop is to pull over, turn the car off, wait a few minutes and then start the car again. Code is a T1529. We thought maybe the Alternator, but the Alternator seems fine. We are thinking Transmission Control Switch. Is this expensive to fix and how involved will this be as we are thinking this part is inside the car back where the radio and AC is located in the car.

Answer
P1529 simply indicates that the transmission control module has requested the check engine lamp to be turned on.  There will be a separate code stored in the transmission control module which should tell you the nature of the problem.  If you can obtain that code (not sure if the code reader your local auto parts store uses can access transmission codes), do follow-up with it here, and I'll advise you how to proceed.  

The problem is unlikely to be the range switch, which is on top of the transmission.  In most cases, the symptoms you describe are caused by a faulty input or output speed sensor.  If you decide you'd still like to replace the range switch, it's located directly underneathe the shift lever on top of the transmission.  It's relatively easy to replace and adjust.