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 Chr

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.