If you a replacing an ECU on a car with a new one, you have to flash it with the right firmware for the vin number of the car. At least that's the case with Chrysler. My friend works at a Chrysler dealership as a tech, and he says that basically anything you now put in on the car, be it something complex, like the ECU, or something simple, like the windshield washer control module, it has to be programmed. If you don't program it, it doesn't work. On BMW M3 you even need a computer to "program" a new battery.
> On BMW M3 you even need a computer to "program" a new battery.
You're "calibrating" the battery. This has been around on BMWs for a long time (my 2008 535xi had this). If you replace the battery yourself and obviously can't program it in, the car will bitch endlessly, but it'll still work.
