I just purchased an 06 250 w/ 5.4 L. The engine light is on so I had it scanned. O2 sensors needed replacing. Did that. Went to O'R and Advanced Auto to clear the codes and a P1633 code will not clear. The engine light comes on after about 10 seconds after starting. It will not pass emissions with the light on. I've read that Ford says that they are the only ones that can erase P1633 code for 100 bucks. I know what the code means but how to solve is my problem. Anyone know if this is true and what are the main things that cause this code that I can check? Battery power voltage is fine. I disconnected it for a brief time the other day and then reconnected. I'm in a dry climate, CO but the truck is from western dusty TX

 

Well, after Ford and the local parts stores scanning and testing, I found out the problem.
Ford scanned, tested and pin-pointed the problem. They showed me a plug at the firewall that had pin 45 with no constant power. The tech said that I could run a jumper from the engine comp fuse box to that pin and solve the prob. Got home and got the tools out. Opened the dusty fuse comp. Pulled a randum #10 -10amp fuse. Hey look, it's blown. Went to the owners guide that I looked at the day before in the fuse section and missed that #10 fuse is for the power train module (pcm) KEEP ALIVE POWER, canister vent selenoid. A vent code was also comming up and all said that it was the gas cap.
Replaced the fuse and holly crap Batman, the engine light went off and the codes are gone.
Un-freakin believable.