check engine p0451, p1702 only when start the car.help
 

Hi,sometimes when I start my focus 2009 the check engine light comes on but the codes only come on when I start the car, never when the car is running, the codes mean "transmission range sensor and fuel tank sensor" my inquiry is why the check engine light isn't permanent on?? Please any idea, Thank You For Response:)

The system runs certain tests on start up only.