Possible Causes

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

Possible causes are:

Battery terminal corrosion or loose connections (P0603 or P1605).
Open KAPWR circuit (P1633).
KAPWR to PCM interrupt/open (P0603 or P1605).
Damaged PCM (P0603, P1605 or P1633).
Reprogramming (P0603 or P1605).
Intermittent KAPWR circuit (P1633).