I decided to fix the problem. The repair should also be applicable to 2000-2005 Buick Lesabre and Pontiac Bonneville. The GM factory service manual was lacking information on troubleshooting this symptom. A quick internet search revealed that the oil pressure sending unit is usually the cause of the high oil pressure reading. I decided to try to install a new oil pressure sending unit. Amazon continues to amaze me on their auto part prices. I ended up with a genuine AC Delco unit, part number 213-1650 for $35 with free two day prime shipping. I'm not an oem part zelout, but the price was right and I know that it would be the correct part.
The threads on the new part came precoated with a thread sealer.
If you place the car on ramps you can access the sensor from underneath. It is a reach, but it can be done. The sensor is located above the oil filter. I had to remove the clip for the electrical connector by feel. Here is a photo of the sending unit from underneath the car:
The GM factory service manual calls for a special socket to remove the oil pressure sending unit, but a plain old fashion deep socket will work just fine. I used a 27mm deep socket. A 1-1/16" deep socket should also work. A while back I purchased a very reasonably priced set of deep metric 1/2" drive impact sockets from Harbour Freight. I amazed how many times I have used these sockets.
Here is a photo of the ratchet, extension, and socket utilized:
A little oil leaked when I removed the sending unit so have a rag ready. The old sending unit was covered in oil. It may have been leaking or there may be an oil leak above.
The torque to install the new unit is 12 ft-lbs. There was adequate room to use a 3/8" drive click type torque wrench. The entire repair took less than 15 minutes. The end result is that the problem is now fixed and the oil pressure reading is approximately 60 psi as shown here:
