Sonata loses power - Limp mode

Hi
 
I am a new owner of 1999 Sonata. Ever since I have bought it, at least once every two days, the car changes gear with a thud and then it loses all its power. It gets stuck in 3rd gear or so. When I change the driving modes to Reverse the whole car shakes. However, when I switch it off, and start again, the car drives incredibly. I took it to the specialists, but they could not find any code when they connected the scanner computer, though physically they too felt loss of power.
 
Does anyone know how to fix this problem? Or atleast, the various possibilities of this problem? Thank you.
 
HyuSon

Do you get a Check Engine Light?  If so, what is the code?  It could be something relatively simple to fix such as a speed sensor.  There are sensors that measure engine rotation, transmission rotation and wheel rotation.  If the signals from those get out of sync, the transmission gets confused and goes to a third gear limp home mode.
 
It could be something more serious, but you need to get it checked.  If you get the CEL code read and it points to a specific sensor, you might be able to change it out yourself and save some money.

Hi Doohickie
 
Thanks for your quick reply. Actually, no lights come up when it happens. No codes were found as well.
 
Thanks.

It is going into 3rd gear limphome due to sensor malfunction.Check codes in Tcm.

I think you need to check each sensor.  Might have to take it to a dealer for that (or buy one of each).

Hi Hyundai tech and Doohickie
 
Thank you both for your replies. I have taken the car to the dealer. Will inform you what they find out.
 
 

Hi Guys
 
The problem was in 'differential speed sensor'. They have fixed it and the car is driving very smoothly.
 
Thanks
 
 

I also have the same problem. I replaced the input and out speed sensors and still have the problem. Can the differental sensor be purchased and installed from someone other than the dealer?
 
Thanks