What do I need to do to my 2003 ford mustang to use the ecm from a 1995 mustang

You can’t, the 1995 is old school OBD1 and the 2003 is next generation OBD 2. Two totally different operating systems.

Answer not posting

It's really easy. Just pull the "03 into the garage, remove the radiator cap, and move the car out. Then move the "95 into the garage and put on the "03 radiator cap. I think that's the only way to do it.

I got some answers for yall 2 first off your wrong about that old system the94 and the 95 was eqipt with an obd2 port And Mr radiator cap guy...have you ever even worked on a car before they probably caught you putting your radiator cap on a empty milk jug full of something called your a total idiot..this is a serios question save your comments for that box at the front of the classroom for guys like you

The v6 which is what I got has obd 2 so can someone give some insight

The 03 is still a different OBD 2 operating system even if the 94 has OBD 2 it is not the same. A hot rod shop might be able to put you in touch with a programmer that can build you an ECM to do what you want but it won’t be cheap if you find one. The only other thing I can think of is if the blocks are the same you can swap 94 engine management hardware to the 03 engine making it compatible with the 94 ECM.

That pre-1996 model was a pre-OBDII and doesn't have the language capable to communicate with an OBDII scanner. It's just an OBDII port with pins for OBDI communication. It was there just because it was more economical to wire the car so transition in 1996 would be easier. Again, the radiator cap thing was for fun, but it's still accurate,

The problem with a 1995 model is it could be EITHER OBD I or OBD II. 1996 and newer is DEFINITELY OBD II and 1994 and older is DEFINITELY OBD I. The style of the connector that you're talking about makes no difference. That style has been used since the late 80s. My (OBD I) 1993 Caprice had one under the dash too. It was called the ALDL (Assembly Line Data Link) connector in those days . Hope that helps! Jim

Damn Cargurus, I posted this 2 days ago..... That pre-1996 model was a pre-OBDII and doesn't have the language capable to communicate with an OBDII scanner. It's just an OBDII port with pins for OBDI communication. It was there just because it was more economical to wire the car so transition in 1996 would be easier. Again, the radiator cap thing was for fun, but it's still accurate,