I bought two new keys for my truck that were suposed to be compatible. When they arrived I noticed they were stamped SA rather than S which indicates they are 80 vs 40 bit. I read that the 80 bit keys are backwards compatible with the 40 bit so I went ahead and had them cut. Unfortunately, I can not get either one to program for me using this method.

https://www.f150online.com/forums/ar...pats-info.html

Has anyone succesfully used 80 bit keys on a 40 bit system, or are they incompatible? I'm not sure whether to buy new keys or just take it to the dealer. Ugh.