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:

Following oil runners are clogged or have leakage:
1. Between oil pressure switch and left side OCV
2. Between left side OCV and left side variable valve timing actuator
3. In left side variable valve timing actuator
Left side variable valve timing actuator is stuck in retard position
Loose timing chain or improper valve timing
Low engine oil pressure
PCM malfunction
Spool valve in left side OCV is stuck in retard position