Low Oil Pressure (shut down engine)

marinegrunt

Well-Known Member
2005 Envoy XL with about 90K. The dic said low oil pressure and to shut down the engine. I pulled over, shut it down, and checked the oil. It was right where it should be. I started it back up and it seemed fine. I was kind of heading down a hill and had to tap the brakes. It flashed low oil pressure just for a second. It didn't come back on. It's now in the garage until I figure it out. I just changed the oil maybe 500 miles ago. We've owned it for almost 3 years and I've always used Mobile 1 Extended and change it around 4000 miles. I'm guessing it's the sender but going to hook up a gauge tomorrow. For some reason my oil pressure tester kit doesn't have the right fitting. Luckily, an old ball joint stud is the same size. I drilled a hole through it, found a nut that fits one of the adapters in the kit, and going to weld the nut to the ball joint stud so I can get a reading.

I realize the test is the number one thing I have to do but just wondering what the main cause usually is for the low oil pressure warning? Is it likely it is the sender? I just get nervous about a low oil pressure reading so need someone to calm my nerves before I go to bed. The wife doesn't notice stuff like that and she's the main driver of it. I just hope it actually isn't low oil pressure and that she hasn't been driving all over with low pressure.

I'll post readings in the morning.

Thanks all!
 

Wooluf1952

Well-Known Member
First; in case you didn't know, the oil pressure guage reading is a lie. It's just an On-Off switch. IIRC, if the pressure goes below 6 lbs., the warning light comes on.
When the warning light lights up, what is the tach reading? If the RPM's are to low, the pressure may be below the 6# level.
At 90k it could very well be the sending unit.
 

Denali n DOO

Silver Supporter
I only saw that dic display once....and it cost me a motor. Good thing you got a 4.2 and probably simple fix due to BS temp gauge.
 

Blckshdw

Moderator
marinegrunt said:
...I was kind of heading down a hill and had to tap the brakes. It flashed low oil pressure just for a second. It didn't come back on....
I thought I saw another thread with your issue, and there was a similar circumstance. Truck pointed down a hill, going into a right hand turn (would require you to brake). I don't know where the pick up tube location is, but I would guess if it's in the rear of the pan, and you slosh all the oil to the front, it may think there's a problem when there really isn't.

I'd say try to replicate the results, since you've confirmed the oil level is correct.
 

coolasice

Well-Known Member
did you check for oil in the electrical connector for the switch? (would positively identify a failed switch)
 

HARDTRAILZ

Moderator
Blckshdw said:
I don't know where the pick up tube location is, but I would guess if it's in the rear of the pan, and you slosh all the oil to the front, it may think there's a problem when there really isn't.
We have a front sump and I know if you go up steep enough stuff it will starve the engine for oil and kick on the light. I did it on this climb
 
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marinegrunt

marinegrunt

Well-Known Member
The oil sloshing around makes sense. My only concern is it has never done it before. I did try to get it to do it again but it didn't.

As for checking the electrical connector for oil I'm pretty sure there was some oil there. I didn't pay attention to it when I removed it so I'm not sure if oil dripped down when I removed the sender or if it was there before. That was something I didn't know to check beforehand. I bet it is the sender though.

I almost have that adapter for my oil pressure tester welded so hopefully that will tell me more. After hearing about the oil in the electrical connector being a sign makes me feel better. I'm 99% the oil blew through the end and didn't drip down.

Thanks guys. I'll let you know what I find out. Have to run an errand so it'll be a couple of hours before I check it. I'll probably bring the old sender with me and pick up a new one while I'm out.

After seeing your pic Hardtrailz I might have to make the wife's Envoy my toy, do some upgrades, and head your way. That looks like a lot of fun. I was stationed out in 29Palms in the Mojave Desert. We all use to off road quite a bit out there. You could about pull off the blacktop anywhere and drive for hundreds of miles without seeing a house or even another road. It was a lot of fun. I think I'd like the wooded muddy trails more though. I've taken the quad out quite a bit around here but never have had a truck for it. I bet that's a blast!
 

HARDTRAILZ

Moderator
Right on. you are the same distance as me from The Badlands basically.
 

bspurloc

Well-Known Member
Blckshdw said:
I thought I saw another thread with your issue, and there was a similar circumstance. Truck pointed down a hill, going into a right hand turn (would require you to brake). I don't know where the pick up tube location is, but I would guess if it's in the rear of the pan, and you slosh all the oil to the front, it may think there's a problem when there really isn't.

I'd say try to replicate the results, since you've confirmed the oil level is correct.
yeah that was my daughters car. It turned out the down hill thing most likely was just a coincidence.
The sensor was shot and letting oil leak back onto its connectors.
Look in at it from the lower area of the passenger tire with a flashlight will show u pretty quickly if your sensor is shot and leaking oil.

notes on when I did hers...
"
I went to advance bought the sensor and looked at their $13 oil pressure sensor socket which was all pretty and stuff then I went to their impact socket area and the $6 1 1/16th socket is the exact same length as the $12 "special" socket. The sensor fits perfectly into the 1 1/16th impact socket.
Only possible issue is its a 1/2" drive but that was not a big deal, more leverage with the longer ratchet.
I put the socket on the sensor first, then reached up and attached the ratchet once broken loose the oil sensor can be taken out with finger strength.
I then took the ratchet off and then the socket because there is a hose in the way.
Unscrewed the sensor with my hand, let the few ounces of oil spill out as I reached for the replacement sensor and screwed it in.
Put the impact socket back on, then the ratchet and tightened it all up.
I cleaned the sensor connector with carb cleaner, then sprayed the whole area to clean up all the accumulated dripping oil and other residue.

NOTE: it did take more effort than I thought it would to get the wire to clip into the new sensor, at first I thought it was the wrong sensor till I realized it was all the rubber sealing holding it back. or maybe there was still some carb cleaner in the wire harness causing extra pressure"
 
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marinegrunt

marinegrunt

Well-Known Member
According to alldata oil pressure should be 12 psi minimum at 1200 rpm's. If 12 psi is minimum what is considered normal?
 

bspurloc

Well-Known Member
marinegrunt said:
According to alldata oil pressure should be 12 psi minimum at 1200 rpm's. If 12 psi is minimum what is considered normal?
Whatever it should be don't look at the oil pressure gauge on this car to see what it is as that gauge is completely useless. as you will see searching it here!
It isnt an oil pressure gauge it is just a dummy light showing useless voltage readings
 
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marinegrunt

marinegrunt

Well-Known Member
I used my actual oil pressure tester. At idle pressure was around 18 psi. At 1200 rpm's pressure was around 30-35 psi. That definitely points to the sender. Since I know pressure is good, and I know it's driveable, I went ahead and ordered an ac delco online. $24 vs $42 for a Dorman or Duralast or whatever the local stores had.
 

nodogs027

Active Member
First; in case you didn't know, the oil pressure guage reading is a lie. It's just an On-Off switch. IIRC, if the pressure goes below 6 lbs., the warning light comes on.
When the warning light lights up, what is the tach reading? If the RPM's are to low, the pressure may be below the 6# level.
At 90k it could very well be the sending unit.
I have 2003 TB. Same symptoms I replaced the switch and everything is back to normal. It took me 10 minutes!
 

BanditGTP

Well-Known Member
I have a 03 Envoy with 213k miles on it. As soon as I got off the highway and came to a stop, my light came on. Just checked and it looks like I have plenty of oil. If it's the sender, do you think I would be OK to do my 20mile ride back home? I really don't feel like taking it to a shop.
 

pL2005

Member
Mine did this in September. Once I checked the oil and verified everything else was ok, I decided to wait until I could replicate the problem. It hasn't done it again. I'm sure I'll have to replace my sender at some point, but until that day comes......
 

Mooseman

Moderator
If it's running OK with no noises, it should be fine. Is it always on or intermittent? It's usually intermittent.
 

BanditGTP

Well-Known Member
It only came on after a 40 mile run on the highway. When I got on a secondary road and hit traffic, it started to come on. I noticed that if I kept the RPMs a little higher than idle, it would not come on so I kept doing that until I got to my destination. After the truck rested for 90min I was ready for the return trip home and it never came on again.

As far as noises....there was nothing new. I guess I'll keep an eye on it and if it happens again, I'll see about replacing the sender. Is it the sensor located by the passenger wheel well? I just took a quick peak and I see a sensor that looks real easy to get to.
 

Kelly@PCMofNC

Well-Known Member
It only came on after a 40 mile run on the highway. When I got on a secondary road and hit traffic, it started to come on. I noticed that if I kept the RPMs a little higher than idle, it would not come on so I kept doing that until I got to my destination. After the truck rested for 90min I was ready for the return trip home and it never came on again.

As far as noises....there was nothing new. I guess I'll keep an eye on it and if it happens again, I'll see about replacing the sender. Is it the sensor located by the passenger wheel well? I just took a quick peak and I see a sensor that looks real easy to get to.
Generally that's not a good sign, the more RPM it has usually the more oil pressure it has, so its possible that you were keeping it just high enough to satisfy the light from coming on. But if the problem comes and goes, it's probably the sending unit...usually if it is something mechanical causing the low pressure, it's always going to be like that (at least when it's warm). You won't really know for sure until you check the pressure with a gauge though. Fingers crossed it's the sending unit!
 

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