So I have a 1996 Mustang 5.0. my mom had bought for me years ago. It sat in her garage over 10 years and I finally moved it to where I live about 2 years ago. About a year and a half ago my ex stole my keys haven't seen the keys or him sense. So, I bought a new ignition cylinder, installed it, of course it took almost a week of attempting to start her before it dawned on me the theft system was cutting the fuel to the engine. so, I was going to take it in to work (i work in a garage) and have our ford guy come fix the key when my tires arrived this week i was going to have it towed in. my boss said i should do some research he believed there could be a bypass and i could save some money by fixing the key myself. so after research i find the same proceedure in several places so i decided to give it a shot. I bought a brand new battery (not reconditioned) installed and followed the proceedure (key to on, theft light blinks, 15 minutes, within 2 after the blinking stops turn key off then back to on blink 15 minutes and repeat total of 3 times or 45 minutes). Excited after the third time, clutch in turn key everything goes dead immediately, every light in the car every sound no turn over absolutely dead key does nothing, no funny sounds or odd responses just lights and life immediately ceased on my mustang with her new battery which looks just fine nothing changed under the hood either. Any takers on what the heck just happened? Looks like I'll be calling our Ford guy anyway. Figured too good to be true.

 

Why not just get a new set of keys from Ford? They can get them based on the vin, as long as the registration is in your name.

Also, if you have a 96 you have a 4.6 not a 5.0 fyi.


The car might just have a bad ground, mine would do the same thing as yours until I replaced the battery leads