Possible Causes

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.

Possible causes are:

EEGR valve stuck open or closed (P0400 or P1408).
Connector to EEGR not seated (P0400, P0403 or P0408).
EEGR motor windings shorted or open (P0400, P0403 or P1408).
No power to EEGR (P0400 or P1408).
Harness open or shorted to power or ground (P0400 or P1408).
Vacuum signal to MAP restricted or leaking (P0400 or P1408).
MAF sensor signal erroneous (P0400 or P1408).
Damaged PCM (P0400, P0403 or P1408).
Carbon buildup in EEGR valve seat (P0400 or P1408).
One or more sensors not responding or out of range (P0400 or P1408).
Open or short in harness from PCM to EEGR (P0403).
Short circuit in EEGR motor (P0403).