A steady check engine light is usually no big deal. If it's flashing it's major... and probably something you can't fix yourself unless you're very mechanically inclined. On the other hand, a flashing light can also mean the engine's misfiring. The light will illuminate at the time when the misfire occurs. If you can figure out why it's misfiring, and you have some mechanical knowledge and some tools, you can usually fix it yourself (lean mixture, [clogged injectors], weak pump or clogged fuel filter [though you changed those], leaky EGR valve [happened to me on one of my Broncos], etc.). You will need a code reader though, to figure out which cylinder is misfiring (if the spark plug won't tell you).
Originally Posted by
Cubdriver
A hundred different things can cause a check engine condition, it could be nothing or the engine could be about to die.
That's true... on some cars, leaving the gas door open or the cap too loose will cause the "Check Engine" light to come on. A flashing light means something much worse. I'd venture to say it's your transmission that's about to die, not your engine. The longer you let it go, the more $$$ it'll cost. Get that truck to a shop pronto!