EGR Solenoid Vacuum Valve
WARNING: This page is about a different car, the 1996 Suzuki X-90. However, it is still accessible from the selected car via links, so may be relevant.
See DTC P0400 in appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in appropriate TESTS W/CODES article.