Check engine light stays on

It may take a while to duplicate the circumstances that put the light on but it will likely come on again.

2007 Hyundai Sonata 6 cyl Front Wheel Drive Automatic

i have a 2007 hyundai sonata v6 the check engine light goes on and off so i bought an obd II tester that works with my car i tested it when the check engine light was off and it read that there was a fault but when i check to see the code it came up as n/a is it because the light was not on ?

Light or no light if its has a stored code/s in it -it will indicate on the reader-you must have erase it-

There is no sensor. The ecm is what monitors parameters and when a component is out of range it will set a code.

Roy