Hyundai Repair: Tucson 2006, transmission control module, engine control module ecm

Question
I have a Tucson 2005.I have recently had this problem where the gear is not changing and its at gear 3 only and the CHECK indictor was ON. I took it to my workshop and was told the error was TMC. Can you please advice me on what this error is. Thanks

Answer
I suspect the workshop meant TCM (transmission control module).  When the TCM sees a problem with the transmission or the sensors necessary to operate the transmission, it puts the transmission in third gear only.  

Unfortunately, there are numerous reasons why this would occur.  To know what type of problem was seen, I'll need to know the trouble codes from the engine control module (ECM) and TCM.  AutoZone and AAMCO have advertised they'll read the trouble codes for free.