The newer installations don't use pressure switches - they use differential pressure transducers (typically strain gauge type). Switches fail (especially in the adverse environment of an engine) - transducers are far easier to fault detect, and monitored by the FADEC they are typically dual channel redundant. Typical installation will set a fault when the delta P gets above a certainly level (if anyone's looking it says it time to replace the filter), then set a flight deck message when the delta P approaches bypass.
All that being said, I don't know what the CFM56-7 uses...