Strange oil pressure gauge reading.

GeoGoGo

Original poster
Member
Dec 29, 2015
166
Upstate NY
Hi Everyone!

I just ran into an issue with my 07 LT. Out of the blue, my oil pressure reading dropped to 0 and I got the 'Low Oil Pressure' and 'Stop Engine' messages. I got scared and pulled over; checked the oil level and it was just a touch below halfway on the cross-hatched area of the dipstick. No leaks anywhere.

I start it back up and the gauge jumps back to 40ish psi like normal. A little while later it does it again, gauge drops back to 0. I listen and there is no valve clatter, no loss of power. No indication of any problem other than the oil pressure gauge. The next day it dropped to 0 again while I was in a drive-thru. That is when I noticed it would drop to 0 at idle (about 600 rpm). If I ran it to about 900-1000 rpm, the pressure would jump right back up to normal. Let it go back down to idle and it drops to 0, blip the throttle and right back up to normal.

I have driven several vehicles with low or no oil pressure and I know some of the readily identifiable symptoms. I am experiencing nothing like I would expect if there was no oil pressure. Is this a sending unit or a gauge issue? Could my oil pressure possibly be as low as the gauge indicates? It has me a little worried.

I look forward to hearing any thoughts, ideas, suggestions, or input. Thank you all for the time and have a great night! Stay safe!

Respectfully,
George D.

Oil Pressure gauge

PS: There is a large truck driving by in the beginning. That is not my TB!
 

TJBaker57

Member
Aug 16, 2015
2,897
Colorado
Hi Everyone!

I just ran into an issue with my 07 LT. Out of the blue, my oil pressure reading dropped to 0 and I got the 'Low Oil Pressure' and 'Stop Engine' messages. I got scared and pulled over; checked the oil level and it was just a touch below halfway on the cross-hatched area of the dipstick. No leaks anywhere.

I start it back up and the gauge jumps back to 40ish psi like normal. A little while later it does it again, gauge drops back to 0. I listen and there is no valve clatter, no loss of power. No indication of any problem other than the oil pressure gauge. The next day it dropped to 0 again while I was in a drive-thru. That is when I noticed it would drop to 0 at idle (about 600 rpm). If I ran it to about 900-1000 rpm, the pressure would jump right back up to normal. Let it go back down to idle and it drops to 0, blip the throttle and right back up to normal.

I have driven several vehicles with low or no oil pressure and I know some of the readily identifiable symptoms. I am experiencing nothing like I would expect if there was no oil pressure. Is this a sending unit or a gauge issue? Could my oil pressure possibly be as low as the gauge indicates? It has me a little worried.

I look forward to hearing any thoughts, ideas, suggestions, or input. Thank you all for the time and have a great night! Stay safe!

Respectfully,
George D.

Oil Pressure gauge

PS: There is a large truck driving by in the beginning. That is not my TB!

So to get you up to speed. There is no true oil pressure sensor in the 4.2 engine. Remember the days of the idiot lights that would flicker at idle when the oil pressure might be a little low on an old high mileage engine? Essentially that is what the 4.2 engine has, a simple oil pressure switch that only has an ON or OFF value. Everything seen on the dash gauge is a calculated number made up by the PCM and based on things like engine rpm, coolant temp and so on. So if the pressure switch is borderline or the oil is old and due for a change or maybe the idle is a little low due to a dirty throttle body, anything like that will cause what you have just experienced. I went through the same thing then I added a mechanical gauge as a backup so I could see what the real pressure value is.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
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TJBaker57

Member
Aug 16, 2015
2,897
Colorado
The previous is not to suggest you ignore the issue. With mine I first off tested the pressure with a real test gauge. If the oil is fresh and the right type have a look at the switch. It is located just above the oil filter. Does it look like it has been leaking? How many miles we talking about here?
 

GeoGoGo

Original poster
Member
Dec 29, 2015
166
Upstate NY
Thank you for the info, guys. There doesn't appear to be any leakage that I can see. I have about 2800 miles on the oil and the truck itself has 186k.
 

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