Looking for the OBD plug for my 04 miata

If you are referring to the car's computer and the light coming on is the 'check engine' light, then you need to find out WHY the light is coming on. If you don't already have one, buy a basic OBD reader (+/- $20 on Amazon), plug it into the OBD port (usually under the dash near the hood release lever) and see what the OBD error code registers. You can then decide what to do. My unit also has the facility to delete the error codes, but when the computer goes through another check cycle, the light will come back on.

If it is OBD-1 you can use a paper clip to jumper two terminals in the test plug under the dash, and then watch the check engine light flash. If it is OBD-2 you need a code reader or scanner.
Most auto parts stores will read OBD-2 systems for free in hopes of selling you some parts.

if your car was made before 1996 yes you can, but car 96 to todays car you can not.

OBD 2 connecotr is usually under dash on driver side. But OBD 2 did not start officially until 1996.

OBD 1 before that. Could be under hood.

The connector is located on the drivers side just above the parking brake pedal.

Hope this helps.

Zeppelinx12

That's easy. Just get an OBD-II compliant scanner. It will support 1996 and up vehicles that were required by law to have an OBD-II connector below the steering wheel under the dash board, in many cases.

Actron makes a good one for under $100. But other brands can be had for under $100 from Sears or Walmart.

Or, you could go to Autozone or Advance Auto Parts, for instance, and get it scanned for free.

Do you have a service engine soon light on?

Good luck on diagnosing and repairing the problem.

There are couple of codes that work on this model of car. It is an OBD I compliant car.

Try visit http://www.actron.com

Good luck.

Any OBD2 reader should work. the OBD connector is under the dash just forward of where the drivers knees would be. I think most ALL cars are within 18" of the steering wheel.

well first you must repair the problem that caused it to come on, u will have a trouble code stored, once the repair is completed the light will need to be cleared/turned off with a OBD 2 scanner.

There should be an OBD II plug under  the dash on the drivers side. It might have a cover over it so look real close. That actron will give you generic P codes.