A method of operating an internal combustion engine that includes a valvetrain having a rocker arm assembly including a rocker arm on which a latch pin is mounted. An actuator for the latch pin, including an electromagnet, is mounted separately from the rocker arm. Rocker arm position information is obtained by gathering and analyzing data relating to a current or voltage in an electrical circuit that is operative to power the electromagnet. The rocker arm position information is used to perform a diagnostic.