Possible causes

– Faulty EGR volume control solenoid valve
– EGR volume control solenoid valve harness is open or shorted
– EGR volume control solenoid valve circuit poor electrical connection
– EGR temperature sensor and circuit

When is the code detected?

An improper voltage signal is sent to ECM through the valve

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Possible engine hesitation

P0403 MAZDA Description

Early Exhaust Gas Recirculation (EGR) systems component s include and EGR Valve, and Engine Control