Diagnostic system for pressure switch

摘要

A diagnostic system is arranged to detect a malfunction in a pressure switch for sensing a negative pressure in a passage between an actuator and a selector valve for alternately introducing a negative pressure such as an intake manifold vacuum and an atmospheric pressure to the actuator to control the actuator. The diagnostic system has a section for carrying out a diagnostic operation on the pressure switch during engine operation, and a section for carrying out a similar diagnostic operation to check the pressure switch after a stop of the engine while holding a power supply for the diagnosis.