Hyundai Repair: Hyundai Tibiron, throttle position sensor, tibiron

Question
The automatic transmission does a hard shift decelerating into 1st gear coming out of 2nd. Took it to the shop and the shop said that the TCM might need replacing. A code came up as P0734. What are your thoughts? I have read something about a Gear 4 Ratio incorrect code. Thanks for any help.  

Answer
P0734 indicates that the transmission is slipping in fourth gear.  Typically, when this occurs, you'll need a transmission overhaul or replacement.

The transmission in your vehicle (depending on model year) should actually not shift into first gear when you come to a stop.  It should stay in 2nd gear until you depress the accelerator to leave the stop.  When the transmission does shift into first gear at stops, it's usually due to an idle switch problem.  Your vehicle doesn't have a separate idle switch, though.  The ECM infers the idle switch reading from the throttle position sensor (TPS) value.  So you might want to check your throttle position sensor to see if it seems to be malfunctioning.

You may also wish to take the vehicle to the dealer for diagnosis.  The dealer's scan tool has the capability of reading the TPS, the inferred idle switch value, the current engaged gear, and other useful data values that will help the technician understand exactly what the transmission is doing and why.  Without that capability, it's either difficult or nearly impossible to diagnose some transmission issues.