My 1996 Nissan pickup's check engine light is on. I had it checked and was told that the O2 sensor was bad. I replaced the O2 sensor and the check engine light is still on.

Always buy OEM sensors.

I called Kia about my check engine light and I told them my mechanic
read the computer and it says 02 sensor. She told me Kia does not sell out there codes to the computer in our cars and that I would have to take it to a Kia repair shop to get the correct reading form the computer

You have a fail exhaust converter on bank # 1

Google the PO420 code & read up

The computer will keep lighting up the check engine light as long as there is a problem with a sensor in the car, which the O2 are. You will have to replace those O2 sensors to get the check engine light to stay off, if that is the only problem with your car. Have the trouble codes read from your car to see if anything else is also bad.

IF YOU HAVE AN NTC TYPE OF COOLANT SENSOR ON THIS CAR , IT CAN BE BAD WIRES TO THE SENSOR , THIS WILL LEAN OUT THE FUEL-AIR MIX , AND MAKE FAULT CODE TYPE 0170-0171 .

Sounds like a bad O2 sensor.

check out www.maxima.org

possibly a spark plug wire loose or plugs need replacing?

bad wiring harnes or someone i know had the same problem, your computer should be on the fire wall, water likes to run under the hood and down the fire wall, check the plug on the computer for wetness or ice, what ever the case my be.

Autozone oxygen sensors do not function properly in Toyota vehicles. Just had a Tacoma yesterday with the same issue. New sensors, runs poor, check engine light on. Toyota sensors fixed it right now.