96' F250 tranny take off problem (engine light)

[benkim]

I have a 1996 F250 7.3L PSD, 2WD auto trans. When i start truck and let idle, either cold or warm, if i press pedal to rev up the motor the check engine light comes on and the motor keeps idling. When i let go of the pedal the light shuts off and motor still idles. This happens sometimes and some other times it will work perfectly fine. When i push on the brake pedal and shift from park to either reverse or drive it will engage like it should. Once i let go of the brake pedal and press the gas pedal the check engine light will come on and the truck will just keep idling. I have to press the brake pedal and shift back into park then back into rev. or drive.Same thing will happen where it will engage but this time it will work perfectly fine no sloppy shifting no slipping. this happens half a dozen times thruout the day. i had someone plug a scanner and the code was 221(i think) and 603. One code was a improper switch code and the other was an internal command switch i believe.He said he had no clue and i was going to see if anyone had similar problems before i go to the local ford dealer,they are a rip off but will know what it is.