Detection Condition

WARNING: This page is about a different car, the 2002 Mazda B4000, 2002 Mazda B3000, and 2002 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0400 indicates EGR malfunction is detected by PCM calculations (EGR flow is less than or more than expected).
DTC P0403 indicates EEGR electric motor windings or circuits to PCM are shorted or open.
DTC P1408 indicates EGR flow is out of self-test range when EGR system is commanded ON.

The Electric EGR (EEGR) system receives signals from the CHT, IAT, TP, CKP, MAF and MAP sensors provide PCM information on engine operating conditions. After vehicle has warmed up and normal EGR rates are being commanded by PCM, EGR flow check is performed. EEGR flow test rate is done by observing behavior of 2 different MAP values (analog MAP reading and inferred MAP). During normal, steady-state operating conditions, EEGR is commanded ON to a specified percentage. EEGR is then commanded OFF. If EEGR system is working properly, there is a significant difference in both observed and calculated values of MAP (EEGR ON and EEGR OFF). EEGR system is disabled if a malfunction is detected.

EEGR assembly is controlled by PCM with 0-52 discrete increments to move valve from fully closed to fully open. A stepper motor electrical test is a continuous check of four electric stepper motor coils and circuits to PCM.