2001 hyundai elantra transmission problem

[ycart]

i have a 2001 hyundai elantra with 85,000 miles on it. it has an automatic transmission. in jan 2009 the transmission was flushed. ive checked the fluid level and its fine. ocassionally the transmission will slip, when it does kick in it does so hard and triggers an amber colored check engine light. when i restart the car the light is gone. what could be the causes of this? is this an indicater that the transmission is going?

[bmcmillon]

Your Speed sensor in the transmission is out. Take it to the dealer. There are a few of them and only a systems check can tell which one is out. My car did the same thing a couple of months ago.