f.a.t.s.

Passkey three is the new fats for chevys and so forth.....

In most fords and chryslers and the new passkey 3 you need to send a frequency up to the factory key cylinder.....(i.e. DEI part number 555u or in some cases 555f) The 555u gets a key locked in a box(which means u lose an extra key) and gets wired into the brain....then a wire gets wrapped around the key cylinder to send the signal to trick the ECU thinkin there is a key in the ignition.....reason for this is becuz the key has a chip in it.

Now passlock/key 1 & 2 take persay a DEI part number 555L   which sorta works the same way but in actuality u are taking the factory wires and wiring up a part to interrupt the system....

There are others like Buicks and Lincolns where u need to test the resistance in the actual key and kinda make your own bypass module with a relay.

All pretty much the same idea...but work in different ways depending on manufacture and Key type......Some 2003 model chryslers can sometimes have a chip or sometimes not....

There are 2 cars that I have run into where u can use any of this bypass equipment u actually hafta order a factory ring collar from the manufacture

I found them in BMW's and Mazda 626 and 929's  where you go and buy a factory ring collar(the same exact part that sits around the key cylinder and you wire it in the car with an extra key taped inside and leave it under the dash.....this works the same as a 555u but can only be done with the factory collar.

I hope i didnt sound to confusing....all the FATS are just new theft detterent systems so u cant start the car without they key

ummm honestly passlock 1 and passlock 2 are quite the same...justpasslock one u need to hook up 1 more wire for it to work(the bulb test wire) I dont knoe the mega difference....

EWS dont differ in operation to tell u the truth

Hondas use the antenna ring and you do lose a key

I dont beleive there are any others.....