Originally Posted By: hlbly
Strike that first item. The correct engine unit is E9SZ-9278-A or Motorcraft SW-2220. The SW-1311 is for vehicles with the electronic cluster.

The Motorcraft SW-2220 is just a normally open pressure switch, whenever the oil pressure gets to a certain level, it closes. That is used with the "fake" gauge and the "real" gauge with the resistor.
1997 Grand Marquis GS - Died
Now have a 2003 Grand Marquis LS