I have a 2002 Kia Optima lx and my oil light pops on and off.

Sensor is on the transmission usually on top but toward the front. Usually held in with a 10mm socket.

i put on a oil pressure switch on my car. which is a 2005 kia optima lx and the oil light still flickering

I had 2006 kia optima 2.4 liter LX, I drove 150000 miles plus, it was over 100,000 miles I changed timing belt, and AC belt, alternator belt is still ok, but it was my fault, I did not change crank shaft balance belt, it next to timing belt, this very important, timing belt and crank shaft balance belt must change same time, you set all mark the same positions, you can see all clear marked
if you had OBD2 scanner is helpful to read all faulty codes if you do it your self repair
if you have any problems about KIA optima, please post on any websites, to share some ideas to other KIA optima owners, like me, I change oil every 2500 miles to make my optima runs smoother
automatic transmission fluid change every year if you put high mileage on your car, optima had hard time to find it own part some time, radiator hoses are still good condition and had hard time to find in any auto part stores in my home town, good luck and thanks for sharing.

check all fluids and change or check oil and filter.

You are gonna have to change the ignition cylinder. Order a new one from the dealership, or from a parts supply store. It isnt very easy to change a lock cylinder.

have your neutral savty switch cheched or may be your relay

The part may be a dealer item only. Not sold in the after market. You would have to try auto parts stores or a dealer in your area. The part is called the tensioner pulley assembly. You would have to check, but on some you get just the pulley and others come with the bracket and everything. Just a word of caution do not go to a salvage yard and get a used one. It is not worth it when it may not last long enough to make it worth the hassle of changing the pulley around. Buy a new one and be done with it.

P0442 EVAP Leak Monitor .040 Leak Detected (Medium Leak)

P0456 EVAP Leak Monitor .020 Leak Detected

replace your gas cap and clear codes, then wait and see if light comes back on, if it does you have a more serious problem like a fuel tank leak or a defective fuel tank pressure sensor.

sgutowski283: the LX had 2 different engines which could have been in you car. However, KIA has engineered their engines to where the oil filter is located at the very front of the engine below the front crank pulley on both the 4 and 6 cylinder engines.
STAY AWAY FROM CHEAP OIL AND CHEAP OIL FILTERS! You engine will last for 200,000 miles easily, if taken care of.
Good luck, Give the folks at FIXYA some feed back if your happy with my assistance.
Thanks.

There is a good chance it could be your fuel pump , however if the check engine light is coming on and the dealer cant tell you what is wrong , try a different dealer or another shop. Second opinions never hurt.