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oil pressure low on the dic

K

kramer56

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Carthage,NY
Hey guys I need some info on my lly that all the sudden has this oil pressure low and dinging on my dic. I ran it saturday afternoon andruns fine, shut it down and a few hours later I pulled out of driveway and this came on, I backed back in and checked oil, full, I don't drive it but had a friend hook a tech II up and it was reading 2.3-3.1psi for oil pressure. we used the tech II and moved all the guages so thinking the guage will move. How many volts does the oil pressure switch need? Today I changed the oil filter thinking something in filter was messed up but still the same thing. I read to remove filter and turn it over to see if oil goes eveywhere and nope it doesn't. The thing is that the engine has no DTC and is full of oil and sounds perfect idling and ramped up to 1200rpm for a few seconds and back to idle then off. Does anyone out there have any insight on this issue and what to do now? I have a new switch on order god forbid a dealer carry one lol. I'm looking for anything here like where would one check for oil pressure with a manual guage, how many ports to check it in too?
 
GM's first step for low oil pressure is to change the oil!

Cut open the old filter and see if it is full of stuff. The DIC comes on at 9 PSI. You only need 13 PSI at idle as I recall. Shifting into gear or reverse to drive will cause a sudden oil pressure drop of ~3 PSI.

Last time I had this issue my oil was 2 quarts high from biodiesel contamination and it was thinning out the oil on the 2008. Thus a big reason GM says to change the oil first. An oil sample can also tell you if coolant is wiping a bearing etc.

Oil pressure switches/sensors are famous for failing. You only need to test there for pressure with a mech gauge.
 
so you are saying that my oil might be too high? it shows full or just above full now since i added a little when this all started happening(im only talking a quart or less). So take out the sensor and check for pressure there or at the filter housing? I need to wait until i have trhe new switch because my luck the old one will break since the under of that truck is rusted, thanks to New York DOT lol
 
I checked the oil pressure with a guage at the filter housing and little oil came out when i pulled the temp probe for my recon guage and the oil pressure guage didn't even move, I am so not getting this? what else to check now guys? I know you're out there guys please something?
 
Change the oil. Oil can have diesel fuel in it and that will thin the oil out to where you loose oil pressure. This is why my high reading of +2 quarts was from biodiesel in the oil and that thinned it out. Engines use oil esp. when thinned out so you can dump two quarts of fuel in and still be down 1/2 quart...

After the oil change verify oil pressure.

Take a sample of the oil as you will need to get it to a lab and see what is in it. bad bearing, coolant, diesel fuel...
 
ok I changed the oil and still no pressure on either guage. I am waiting for the new pressure sensor/switch to arrive but I doubt that the problem right? Any ideas now guys? Anything?
 
I've never heard if a DMax oil pump failure but I suppose it's possible. I've seen it happen on gasser motors before.
Sure hope that isn't it though...
 
I want it to be my last resort to be honest. Would the motor knock and sound like its coming apart at idle even if no oil pumping thru it, I even ramped it up to 1500rpm and the turbo whistles when i let off and everything. It purrs like a kitten just as it always does, nothing a different
 
kramer56 said:
ok I changed the oil and still no pressure on either guage. I am waiting for the new pressure sensor/switch to arrive but I doubt that the problem right? Any ideas now guys? Anything?
Click to expand...

What oil did you use? 5W40, or 15W40? I believe the Duramax's use a low pressure, high volume oil pump. I am not sure if that change was made in 2006, or earlier. How many miles do you have on the odometer? It probably is just an oil pressure sending unit gone bad.
 
well i thought that so i ordered a sensor, but why nothing on a oil manual oil pressure guage tapped into the port on filter housing? I always winter/summer use 15W/40 for diesel engines
 
The gear has been know to spin on the shaft. I would try to hook your gauge up to the same port as the sensor is in and go from there.
 
how do you get to that gear, pull the motor? if that spun on the shaft does it mean new pump? boy this sucks being desperate lol
 
Put your mechanical gauge on the oil gallery port on the block. That is your best bet. And if that truck has not rattled itself to bits with the gauge displaying zero then odds are you have oil pressure. The sending units are known to go out on these trucks as well as the stepper motors in the cluster.

K.I.S.S.


Oil pump gears USUALLY spin after prolonged exposure to high rpm. Thinned oil will still show pressure, (insert some dead scientists law here)

replace sending unit and while waiting put your mechanical gauge on an oil galley port on the passenger side of the block.
 
Ok, I have an 05 LLY with almost 200K on the clock, This truck had a rough life previous to my ownership. I have always maintained this truck to a "T" and it has treated me very good. Last October a friend took it to Mich to pick up a 36' Baja and bring back to NY. On the way out after stopping for fuel and food he started the truck and dash showed no oil PSI and DIC said "Low Oil Presure". On the way back the guage would read fine then read 0psi and never missed a beat. Ordered a new sending unit (still yet to install and a year later) and fro a few months showed normal PSI and now agin shows nothing for PSI at this current time. I'm sure in my case its just the sending unit as for I have put 30K on it like this. The only mechanical issue I've had has the fuel cooler under the drivers bedside rotted out and was leaking so I bypassed it. Other then that this truck is GREAT and I love it, even though it is the undesireable x cab long box, and get 20mpg with the Hypertech Programer. I did buy a new updated dash from United Radio in Syracuse just to make sure the guage wasn't bad, we did install and unistall the hypertech a few times and that would somtimes trigger the guage to work/stop working. Good luck and I say drive it for now, you would know if you didn't have PSI for sure.
 
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Like Chevy Silverado Man said Welcome to the Truck Stop Haulin Gas!

It may not be a bad idea to start your own thread if your having troubles. Or feel free to start a thread in the introductions section to better introduce yourself. Nothing sucks more than trying to fix two individual problems in one thread that aren't on the same vehicle, because lets face it, not everybody is going to have the same problem.
 
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