Here is a problem that occurred with me and my 89 F-150. I had the check engine light on the dash flashing intermitently. It wouldn't stay on constant and would catch your eye.....The truck was running fine and I couldn't figure the problem. I spoke with several mechs, some of which work for Ford dealerships. They researched and all I got from them was that the light should not come on and flash,only, if there was a problem, come on and stay on. Hmmm. Weird. I bought a code reader for the truck and ran it through the diagnostic. It inicated the exhaust/thermactor system as a problem. Not very specific, but at least a place to start, huh? Anyway. I slowly worked through the system replacing everything starting with the air bypass valve,EGR,o2 sensor, thermactor tree, everything I could think of....Still my light continued to flash away on the dash and blew my mind. It got to the point where there was nothing else to replace and I basically just ignored the thing and business as usual. The coder still read a exhaust/thermactor problem. That was impossible since everything was now new. On one bored day I decided to clean the clear panel on the dash to get the 8 years of dust out and just to 'do something with the truck'. You know. Gotta be doing something. Anyway. Appart came the dash. Got everything cleaned and looking good and put back together. I even cleaned the idiot light bulbs behind the panel replacing those that "looked" ready to go. WELL, I be dog gonnned that the light never came on again. How bout them nanners!!!! This hasn't happened with my 250 as of yet. but if it does, I sure know how to fix it this time. Replace everything under the hood relating to or connected with, your engine. Then, check the bulb and make sure its not loose. Unreal, huh? I saw something on the light and thought I would throw that experience out there for GP. Rob

 

Mine DID come on. 99.5 v10 sd. I hard-booted the PCM last night and it hasn't come on again, yet that is. Now I just have the ABS light to deal with.

Rob