An internal combustion engine includes a cam-actuated rocker arm assembly with a solenoid-actuated latch that provides for cylinder deactivation or variable valve actuation. The solenoid has an inductance that varies significantly in relation to the position of a latch pin as it translates between latching and non-latching configurations. A sensor is positioned to monitor a current or a voltage in a circuit that includes the solenoid. Diagnostic information relating to the operation of the rocker arm assembly is determined by comparing data collected from the sensor over a first period to data collected from the sensor over a second period.