When you say half a head, are you referring to only one side of the engine? If so, which side? When the light turns on, are there any noises such as a ticking or knocking from the engine? If there are no noises, the oil is clean and full, and no other symptoms, try replacing the oil pressure sensor. It is right near the oil filter. Something may have hit it and damaged it.
Just disconnect the sensor and it will screw out and the new one back in.
Let me know.
Monday, December 2nd, 2019 AT 6:32 PM