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:

Connector or terminal malfunction
Open circuit in Green/White wire between VAD control solenoid valve harness connector terminal "B" and PCM 30-pin harness connector terminal "4C"
Open circuit in White wire between main relay and VAD control solenoid valve harness connector terminal "A"
PCM malfunction
Short circuit to ground in Green/White wire between VAD control solenoid valve 2-pin harness connector terminal "B" and PCM 30-pin harness connector terminal "4C"
Short circuit to power in Green/White wire between VAD control solenoid valve harness connector terminal "B" and PCM 30-pin harness connector terminal "4C".
VAD control solenoid valve malfunction