I have the exact same problem with the Low oil pressure warning and the gauge dropping to 0 at idle. It usually happens after driving at least 15 minutes and the engine is warm, when you stop at a red light or stop in the driveway and it drops to idle.
It first started over a year and 20,000 miles ago. I changed the oil pressure switch a year ago but it still did it randomly and has become more frequent lately. Tried changing the pressure switch again but it didn't solve the problem. Since the morons at GM put a bogus oil pressure gauge system in these trucks, I can't tell what the oil pressure is really doing.
I have been trying to find the problem for over a year, although I haven't thrown a oil pressure gauge on it. I might do that when I get time, just to see what I find on pressure but I still think it is a short in the circuit somewhere. Has anyone, traced the wires from the sensor back to see if one of them goes to ground and tried cleaning the ground? I am going to check that out this weekend. Otherwise, I think I am just going to build a jumper plug with a resistor for the pressure sensor connection and just take the sensor out of the equation to see if that will at least get the warnings to stop coming on every time we stop at a light.
Oddly enough, if memory serves me, I believe mine also started doing this after I cleaned the throttle body as I have seen others mention. I don't know if there is a correlation or not but it sure is one hell of a coincidence.
You would think that if it was really losing oil pressure, it would have started having an impact on the engine by now but the engine is still running smooth, quiet and still runs great. I got irritated the other day when it did it at a couple of red lights and I ran it through quarter mile runs off the lights as hard as it would go and it runs like new. I was tach'ing it up to over 5k rpms through the gears, pretty much just hoping it would come apart, but it continues to run just fine.
This trailblazer has been nothing but trouble since I first got it brand new in 2002. It had so many recalls, I lost count. It was at the dealer for a problem every few months the entire time it was under warranty and since the warranty ran out, I have had to work on it myself at least every 6 months but most of the time its something every 3 months. Its so bad that at times, I let things go for a couple of months so I can fix 2 or 3 things at once.
Thanks to this piece of junk, I finally quit buying American cars. I have been buying used Honda's and now have a Mercedes. Funny thing, the used Honda's and Mercedes are better and more reliable than any brand new American car I have ever had. We bought a used 92 Honda Accord back about 6 years ago when gas prices started going up, just to save on gas and we haven't had a bit of trouble out of it. lol
Sorry for the rant, but I am so sick of this trailblazer, I can't hardly stand to look at it anymore. It is my wife's vehicle and I have been trying to talk her into getting rid of it and buying a different car but she doesn't want to have to make car payments. Therefore, I keep having to work on this piece of junk. I think I am getting close to having her talked into it though. :hissy: