DTC P0403: EGR Valve Control Circuit Malfunction: Condition

WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when KOEO of KOER self-tests are being performed, Powertrain Control Module (PCM) detects voltage value from EGR valve is more or less than programed value. Possible causes are:

EGR valve malfunction.
Short or open circuit between EGR valve and PCM.
Open circuit between main relay and EGR.
PCM malfunction.