Rodeo is using oil but there is no evidence of where its going. What is wrong? on 1999 Isuzu Rodeo

There is no spots under the Rodeo of oil leak and it is not smoking from the exhaust. It may occur after maybe 300-400 miles. When the oil gets low the Check Engine light flashes but doesn't stay on.

Asked by for the 1999 Isuzu Rodeo
Pcv valve check this
A hose that is connected to your intake to your valve cover