I have an 02 F150 that will usually start, but now and then the engine will crank but not start and the theft light is flashing like mad. I didn't buy the truck new and only have one key. I can buy a new key and tumbler set from Rock Auto for under $65, but do I then have to take the truck to the dealer to have it "flashed" so my truck will start? Any and all help much appreciated!

 

Yes. A couple caveats:

My guess is that the chip in the key is going bad. It happens.

If you have a dealer installed remote start, you can buy a new key ($12) and get it cut (~$5) and use the intermittent key and remote start to program the new key.

A dealer could make you a key and re-program both of your keys (then you could buy a third key, program it and then get rid of the bad one if it works intermittently enough).

Otherwise you could buy the new tumbler and key set and have the dealer flash your PCM to accept the new keys. (most expensive route).

 

I have a local salvage yard where I can get the ignition lock and 2 keys (if I can find one ) for $7. I checked on-line for a list to see which Fords I can get the correct lock from. Then it's off to the local locksmith shop ,who has the correct equipment to program my "new" keys and lock at a considerably cheaper price than the dealership. Thanks for the info!!!