Multi-step valve lift failure mode detection

A control module comprising:

• an intake air pressure determination module that determines first and second intake air pressures in an engine having intake valve lifters that selectively operate intake valves in first and second lift modes, said first intake air pressure corresponding to an intake stroke of a first piston of said engine when said engine is commanded to operate in said first lift mode and said second intake air pressure corresponding to an intake stroke of a second piston of said engine when said engine is commanded to operate in said first lift mode;
• an intake air pressure comparison module in communication with said intake air pressure determination module that determines a difference between said first and second intake air pressures;
• and
• a lifter failure determination module in communication with said intake air pressure comparison module that diagnoses a lifter failure when said difference exceeds a predetermined limit.