Does the engine have a ticking noise or misfire when started?
How many miles on the engine?
Unplug the connector at the oil pressure sensor and make sure there is no oil leaking at the sensor. If there is then you need to clean the connector and replace the sensor. If there is no oil then check the connector to make sure there are no broken wires and the terminals inside the connector look good. If the connector is good, then replace the sensor. Its shown below in the diagram, the connector is number 4 and the sensor is just below it. Its located at the rear of the engine just towards the front side of the car.