An EVAP fuel tank pressure sensor is a device that monitors the pressure in a vehicle's fuel tank. The sensor is usually located in the tank, near the fuel pump. The sensor sends a signal to the engine control unit (ECU), which uses it to regulate the fuel system.
The EVAP pressure sensor is used to detect leaks in the evaporative emission control system (EVAP). The EVAP system prevents fuel vapors from escaping into the atmosphere. If a leak is detected, the ECU will activate a warning light on the dash board.