Discuss your 2000-2005 Bonneville SE, SLE, SSEi, Buick Le Sabre 00-05 and Buick Park Avenue 97-05. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.
Probably the oil pressure sender, which is a known painpoint in these cars.
~Randall~
1993 Buick Park Avenue - 197k - Some odds and ends done - Simply won't die
1994 Buick Regal - 78k - Bone stock - Always ready for a good kicking
1990 Oldsmobile 88 - Gone to a better place
Would suggest doing along with an oil change. If you remove the sensor prior to draining oil, it will lose oil thru that port. Not a big deal but easier to do with the oil drained regardless.
Like stated above a pretty easy job with the oil filter off.
I bought a 27mm deep socket which made the job a lot easier.
Usually that sending unit goes bad and the oil pressure gauge reads all over.
Girlfriend's LeSabre had the pegged oil pressure gauge problem. Then one day it started using oil. When I changed the oil, I changed the pressure sender (it's right above the oil filter). It was pretty slimy so I suspect it was leaking. Engine hasn't used any oil since.
It was a bit of a pain, but I used an adjustable wrench. Took maybe 20 minutes to get it out due to limited area for wrench movement. I used the BWD brand sender from Advance Auto. It's been in since May and so far so good.
I replaced the oil pressure sending unit on my 2000 SLE about 1,000 miles ago, and since then have not had to add a drop of oil. I had been going through a quart about every 800 miles from a slow leak some place or other or burning oil. But it now seems it was just leaking at that oil pressure switch. I bought the AC Delco one and a $6 socket to fit it from Amazon.
Favorite other cars I've owned:
2003 Lincoln Town Car, Cartier Edition (still have it)
1996 Chevrolet Impala SS (favorite car ever)
1995 Corvette
1989 Toyota Supra Turbo with 5-speed
1979 Mercury Colony Park Station Wagon
1974 Pontiac Trans-Am (455)
1957 VW Beetle
1957 TR3