Hyundai Repair: 1999 hyundai sonata, throttle position sensor, transmission control module tcm

Question
QUESTION: hello ,hpe all is well , ,regarding my 1999 sonanta and gear drops to 3rd from over drive,,is it possible that the tps iasnt working well, or should i be looking else where,,when the tranny works it never misses a beat,,just at times and jerks the car real bad,,thanks

ANSWER: Hi, Gary.  The throttle position sensor is one possibility, but there are many.  The most frequent causes are the input and output speed sensors.

I'd expect that your check engine lamp has been coming on.  There should be diagnostic trouble codes in the engine control module (ECM) and transmission control module (TCM) which will indicate the nature of the issue.

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QUESTION: thanks for the reply, and no i havent had any engine lamp come on at any time,,so yes i was thinking of the TPS seems to not speed up or down propper,,thanks what do you think

Answer
If your check engine lamp is operational (it should come on for a few seconds when you turn the key to the on position), the fact that it does not come on is an indication that the TCM has not put the transmission in 3rd gear due to perceiving some sort of problem.  This makes the TPS scenario much more likely since the TCM determines which gear is appropriate based partially on input from the TPS.  Still, I'd feel better if you were able to retrieve a diagnostic trouble code from either the ECM or TCM that indicated there was an issue with the TPS signal.  This would at least support your theory.  Without that, I'm afraid this isn't much more than an educated guess.  On the other hand, I don't have any more likely alternative to offer based on the information you've been able to give me.