The ZD30 Motor has 2 oil pressure switches a 15psi one and a 25psi one.
It is not Un-Common for them to give trouble and cause the oil warning light to come on

On the Direct Injection motor they are different from one side to the other.
This is the one fitted above the starter motor on the drivers side. The 15 psi one is fitted on the passenger side.

Warning: if your oil warning light comes on, DO NOT assume there is a fault with your switch, and have the oil pressure checked properly before driving the car.