Oil pressure indicator donor

Hello, everybody.

have my eyes like o.a. Part of it looked out, but did not come to a certain result, which encoder on the engine is responsible for the oil pressure indicator...
The display in the instrument cluster goes to full power with the ignition (start of the engine) and remains there until the engine is switched off. I suspect a defective donor is a cause and would like to renew it.
Where does he sit and are there possibly other common causes for this error?

Thank you
Thorwald Brandwein