Catch all tag which can refer to the "brain" of the car which can control the engine and/or transmission of the vehicle. This would include such terms as PCM (powertrain control module), ECM (engine control module), PCU (powertrain control unit), ECU (engine control unit), and many, many others.
(mid-90's Buick) Someone I know had an ECM injector drive output go bad. He got a replacement ECM online, but had to take it to a shop (not a dealer) to get it 'initialized' (If that's the right word....
the Renault/Dacia Logan 2014 and above have indicators like this: As you can see, the dial at the right has the total mileage and the fuel indicator only. I'm wondering if there is an indicator for ...