Damaging an enemy ship's systems in a battle reduces their capabilities, the same as them doing damage to your ship's systems does. However, unlike everything else on a ship, the only function Sensors have in battle is providing you with more information about the two ships.
Does damaging an enemy ship's Sensors have any effect on their ship, aside from giving its crew something else to repair? Given that enemy ships never seem to be selective about what they target on my ship (e.g. uselessly attacking empty rooms with ion weapons), it's not at all obvious to me what use, if any, enemy ships actually make of Sensors.