Possible Causes

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Possible causes are:

CKP sensor malfunction.
ECT sensor malfunction.
PCM malfunction.
Short circuit to ground Blue/Orange wire between VTCS solenoid valve 2-pin harness connector terminal "B" and PCM 30-pin harness connector terminal "4T".
TP sensor malfunction.
VTCS shutter valve actuator malfunction (stuck closed).
VTCS shutter valve malfunction (stuck closed).
VTCS solenoid valve malfunction.