Hello to group and thx for the add.
I purchased a 1999 Chevy Express with Four Winds camper. Everyone looks and run great. HOWEVER.
1. When I turn the key to accessories on a cold engine, the oil gauge indicator goes to the 5 o'clock position (ENGINE OFF).
2, When I start the engine the guage read about 32 lbs. All other guages are reading OK
3. When the engine warms up AND idleing the oil guage reads 0 lbs and the CHECK GUAGES light comes on.
4. When the engine warms up AND over 900 rpm, the oil guage reads 20 lbs and the CHECK GUAGES light is off.
At no time do I get an increase in engine temp OR DTC code indication. On a recent trip from SoCal to Las Vegas everything ran normal and I monitored the OBDII readings the full trip with no abnormal indication.
HELP ANY THOUGHTS, RECCOMENDATIONS, IDEAS, EVER HAD THIS BEFORE? THX

 

I have the same problem in my ‘02 Express 1500. Low oil pressure at idle once the engine warms up/reaches operating temperature. I haven’t had time to fix mine yet, but it’s either a bad gauge, bad pump, or worn out bearings in the engine. Talking to a mechanic, the odds of it being a bad engine are pretty good, unfortunately 😰

 

I ended up having the oil sending unit replaced. It is located toward the rear of the engine under the "turtle" cover located in the driver/passenger area. Replacing the sending unit stopped the leat and my pressure is consistantly between 20-40 lbs.

 

That is the first thing I plan to check/test. I hope that is the problem, because it’s the cheapest and easiest to fix👍👍

 

I learned with my 2002 it will run fine with that sensor entirely unplugged. When warm sometimes it would drop low enough to light the check gauges light, but it drove fine. When I got a no-start I thought maybe it was the computer wouldn't start it because it showed no pressure, but it turned out to be something else.

Some model years have a mesh filter in the port to the sensor which gets clogged and causes low or erratic readings.

 

My problem turned out to be a bad oil pressure sensor. It was leaking oil into the electric connector socket and that would result in the artificial low oil pressure readings when the engine/oil got to operating temperature.
I replaced the sensor with an AC DELCO OEM replacement and, after soaking the mating electrical connector in IPA to remove all remnants of the leaked oil residue, my idle oil pressure levels returned to normal.
From what I have read on this issue, it is not uncommon for these sensors to fail and leak oil into the electrical connector housing. If you have low idle oil pressure once the engine warms up, check the oil pressure sensor for signs of an oil leak at the connector housing.

Peter