What is a module in a car?
A module is a small computer that runs one specific part of the car. A modern vehicle carries between twenty and a hundred of them, each minding its own job: one for the engine, one for the airbags, one for the doors, one for deciding whether your key is accepted. They all talk to each other over a shared wire.
There was a time when pressing a button closed a circuit and that was the whole story. Today the button sends a message to a module, the module decides, and the module acts. Which is why a car that will not start can have a perfectly good engine: what failed is the thing giving the order, not the thing carrying it out.
Modules arrive blank from the factory and get married to ONE specific car, with its VIN and its codes written into them. That is what stops you swapping one between two identical cars: they are the same part with different memories.
When a module gets wet, burns out from a voltage spike, or simply ages, there are two roads. Repair it and load its memory back, or fit a new one and program it from scratch for that car. A general mechanic usually sends this to the dealer, because it needs diagnostic equipment not every shop owns.
The word you will hear next to this one is "programming": the step that teaches a new module who it is and which car it lives in.
Where this comes from
Also in the glossary
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