The engine controller may command an oil-pressure-control state and then evaluate whether the expected electrical, hydraulic, or feedback response occurs according to the engine’s design. Depending on the platform, this may involve actuator-command monitoring, pressure-sensor or switch feedback, calculated pressure plausibility, pump/valve control logic, or combinations of these. P06DD indicates that the requested control response was not achieved or was interpreted as remaining in an unintended state. Exact monitor logic is manufacturer-specific.