1.Locate the oil filter housing.This cylindrical part houses the oil filter and is located near the top of the engine, usually on the front or side.
2.On 2003 E320, the oil pressure switch is located on top of the oil filter housing.
3.There are many different type of oil pressure switches. Some are screwed into the oil filter housing, while others plug into a connector at the top of the housing.
4.Disconnect the oil pressure switch's electrical connector by pressing down on the locking tab and pulling the connector straight up and off.
5.Use an adjustable wrench to loosen and remove the oil pressure switch.
6.Apply a thin coat of oil to the threads of the new switch.
7.Install the new oil pressure switch and tighten it until it is snug.
8.Reconnect the electrical connector.
