Found this online:
Finding the part was virtually impossible. I obained a copy of the GM shop manuals to locate it in pictures and diagrams. Even with them it wasn't easy. To find and replace the part, you will need to raise the front end of the car (Use stable Jackstands on both sides of the car...work safely). I didn't find any way to reach the part from the engine compartment.
Engine position. For directions about where to find the part let's use the following: 1) Engine "forward" is where the serpentine belt is. Forward faces the right wheel well..(passenger side). 2) Right side of engine faces the firewall. 3) "Front Half of engine" is closer to right wheel, "Rear Half" is closer to left wheel (driver's side).
1) Laying on your back looking up , the part can be found about 1 to 1 1/2 feet up from the frame on the Right Front Half side of the engine block. (wear glasses to protect your eyes from falling crud)
2) There is a wire connection with a locking clip holding the connector onto the oil pressure sensor switch. There are 3 connections inside the plug. Remove the connector. If you cannot see the locking clip, it's probably on the other side, out of your sight.
3) You'll need to navigate a 1 1/16" 6 point deep well socket over the part. To get to it you'll need to work around the frame.
4) Once the socket is on the part, I connected a 3" extension to the socket and a socket wrench with a flexible head to the extension. (I happened to use 1/2" drive...3/8's may work)
5) Loosen the part enough to hand turn it out, then remove the wrench, extension, and socket....you may need to take them off one at a time.
6) Remove the part by hand, install the new part by hand (it's brass so be careful), tighten it down with the socket wrench, connect the wiring connector and you should be good to go.
7) Start the engine and check the pressure. It should be reading something other than 0 or 131.
I hope this works for you.....if you can find an easier way, that would be great.
I just wanted to provide a much simpler way to change out the oil pressure switch on the 2001 Aurora with the 3.5L.
1 - Jack up and support the right front of the vehicle.
2 - Remove the right front tire wheel assembly.
3 - Unclip the oil pressure switch harness. When you look into the RF wheel well you will see the oil pressure switch on the rear of the engine, right above the outboard CV shaft boot about 3" - 4". You can reach in the wheel well opening and unclip the harness.
4 - Remove the oil pressure switch. I used a 1-1/16 inch socket, swivel, two 8-inch extensions and the ratchet to remove the switch. I ran it between the convertor and frame rail and guided it through the wheel well opening onto the switch.
5 - Install the new switch, torque to spec, and reclipp the oil pressure switch harness.
6 - Reinstall the wheel, torque to 100 ft-lb, and remove the jack stand.