Check engine light is on in my 2005 Elantra newly maintenanced

P0700 Transmission Control System TCS Malfunction

You can check this website you find there fuse box diagram and description for Hyundai Elantra (2005) and others

http://www.autogenius.info/hyundai-elantra-2005-fuse-box-diagram

if im not wrong it should be with tail lights but i think u have 2 panel boxs also

have someone check the tps sensor

go to autozone n use ther OBD2 for free and haynes repair manual has all the codes.

Driving down several hills today and my car decelarated. It would not coast. I had to use gas going down. This happened yesterday as well. Today, the check engine light came on

will be some sort of engine management sensor, unfortunatly will need to be plugged in to fault diagnosis computer.

The Hyundai online shop manual and my newly arrived Hyundai shop manual kept pointing to the coil as a possible problem. While preparing to check coil continuity I discovered the pigtail connected to the bottom of one of the coils was loose and the contacts were burned. This is the coil that supplies spark to plugs 1 & 4, the same ones that kept showing up each time the check engine light illuminated. After cleaning the contacts and making sure the pigtail was securely attached to the base of the coil I have had no further problems.

Do you own a DMM - digital multi-meter ? Do you know what a wiring diagram is an how to read one ? Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. Year , make , model an engine size. Under system click on lighting, then under subsystem click on courtesy lamps. Click the search button then the blue link . First diagram , look at the right , you will see trunk room lamp .At the top you'll see the fuse the supply's power to the lamp . Check for B+ voltage going in an out , check the switch .
Electric Testing Techniques You Need to Know

I would take it to another Audi dealer or call Audi customer relations at 1-800-822-2834 and see if they can resolve it.