[ScubaSteve1994]

Just got brand new engine installed and plugged in. Fired it up and ran fine for about 5 minutes, the RPMs dropped extremely slow when I touched the throttle. Then after about 10 minutes the "check engine" light came on. I tried plugging in my code reader and all it said was that there was an error connecting, so I ran a module test on my code reader and it gave me a code (B1342) that my ECU was bad.
Talked with a gentleman at a Mustang shop earlier, he said that I have to get an ECU from same car then have a locksmith come and program the computer to the key.
Is this true? If so, how should I go about this?
This is my first Stang and I've been busting my rear to get her going, I need help lol

 

[ScubaSteve1994]

were there any other codes?

that code can be triggered even though PCM is fine

There was one that said low battery voltage. Brand new battery and no pinched wires. When I first got the car, the previous owner had it pulled out already and they broke the plug in the back for a tuning chip, so theres been exposed computer boards and obvious tampering. Ordered the new one from Oreilys yesterday, Ford says the one that goes in these cars is obsolete.