Systems and methods for determining the presence or absence of deposits that may accumulate within a compressor recirculation valve positioned in parallel with a turbocharger compressor are presented. The systems and methods adjust actuators to maintain engine operation such that it may be more difficult for a driver to become aware that a compressor recirculation valve diagnostic is being executed.

Methods and systems are provided for improving surge detection and mitigation. In one example, a surge detection method may selectively filter an aggregate of temperature-adjusted manifold pressure and boost pressure in a frequency range indicative of surge to reduce the effect of non-minimum phase behavior of throttle inlet pressure on surge detection. In addition, the noise contribution of particular engine actuators on throttle inlet pressure in the selected frequency range may be accounted for, reducing the occurrence of false surge indications.

A control device to detect abnormality of a supercharging pressure sensor accurately in an internal combustion engine equipped with a supercharger that can change a supercharging pressure by operation of an actuator. The control device operates an actuator so that a supercharging pressure measured by a supercharging pressure sensor becomes a target supercharging pressure, acquires a measured value of a flow rate of air flowing in an intake passage, and calculates an estimated supercharging pressure based on the measured air flow rate. The control device sets a first abnormality flag when a first simultaneous inequality is established, which is a simultaneous inequality evaluating magnitude correlation between the measured supercharging pressure, the target supercharging pressure and the estimated supercharging pressure, and is not established when the supercharging pressure sensor is normal.