The ECU uses the coolant temperature sensor's input to determine the engine's operating temperature. When the engine is cold, the sensor signals a low temperature. This signal triggers the ECU to implement a richer air-fuel mixture (more fuel relative to air) and/or adjust other parameters like ignition timing to:
* Improve cold-start ability: A richer mixture helps ensure complete combustion and proper warm-up when the engine is cold, because cold engines don't always burn fuel efficiently.
* Prevent engine damage: Cold metal parts are less lubricated and more prone to wear; providing a richer mixture eases this stress during warm-up.
So, while the sensor doesn't directly control the fuel injectors, its reading is a fundamental input to the ECU's strategy for managing fuel delivery during cold starts. The ECU is the actual controller in this process.
