Hyundai Repair: Elantra 2002 transmission, transmission control module tcm, transmission control module

Question
I have the same transmission problem as one of your other readers, transmission THUMPS when changed to R or D and stays stuck in 3rd.
I replaced the TDM and the problem remains.
I saw an answer about changing a wire INSIDE the transmission. Can someone inform me where to buy at a good price.
I am in Canada.

Answer
Hi, Jacques.  There are many, many issues which can cause a transmission to thump and then stay in third gear.  Basically, any time the transmission control module (TCM) sees an issue it thinks will keep the transmission from shifting properly, it will place the transmission in third gear.  This is to both allow you to drive the vehicle and to prevent damage to the transmission.

Presuming your TCM is purposely shifting the transmission into third gear, the first thing you should do is have the TCM interrogated for trouble codes.  Most national parts chains in the U.S. will read diagnostic trouble codes at no charge, but some code readers may not be able to read the codes from the TCM.  It'd be my recommendation to take the code they give you and report it back here.  If you cannot find a place that can do this for you, your money will be best spent at the Hyundai dealer or other very good diagnostic shop on a diagnosis.  Once you have an accurate diagnosis and estimate in hand, it'll be much easier to decide whether you wish to pay to have the repairs done or attempt them yourself.

If you nonetheless desire to replace the wire harness inside the transmission, I doubt you'll be able to purchase the part anywhere other than the Hyundai dealer.