DTC P0404 - EGR Range/Performance Malfunction: Condition

WARNING: This page is about a different car, the 1997 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when EGR valve does not achieve target position during EGR solenoid valve operation. Possible causes are:

EGR solenoid valve (vent) malfunction.
Open or short circuit between terminal No. 4G on Engine Control Module (ECM) connector and terminal "B" (Green wire) on EGR solenoid valve.