Oil Pressure Gauge

[Broke(n)]

So last week, wife tells me oil pressure gauge drops on freeway and that check gauge light comes on.
I did the cheapest solution first and that was I replaced the oil pressure switch (Duralast Oil Pressure Switch PS407). The issue still remains.
The truck is running fine. No leaks. No funky noises. So whats next to check? This is a daily driver 04' XLS Flex Fuel

 

[LMHmedchem]

If this is a v8, then the issue is most likely that the wire to the oil pressure sensor has been worn though.

See this thread here by KC10Chief,

Have a 4.6L? Here's a problem I bet you all have...

This is a bit of a pain to fix since the wiring harness needs to be disconnected in several places that are not that easy to get to. If you go under the front and remove the oil filter drip tray you should be able to get a good enough look at the wiring harness to confirm that this is the issue. The wire the goes off to the pressure sensor is the first one right there. You would have had to remove the connector when you replaced the sensor. Inside the harness, the wire you are looking for has white insulation and is the smallest gauge. The yellow wire to the AC compressor clutch will be the next one to wear through if it hasn't already.

It's not a bad idea to replace the oil filter adapter gasket if you are in that area, especially if you have to drain the oil. You have to drain the engine coolant as well but if you have the oil out you are halfway there. This gasket will leak eventually and I like to replace things that are in an area where I am already working.

LMHmedchem