Gearhead Jim

Recently I happened to have the DIC readout on Oil Pressure, and did the "Run but Don't Start" thing with the start/acc switch.

When everything came to life, the DIC was showing 3 psi and the needle gauge was indeed slightly above 0. The engine had been off for several hours.

Normally, I wouldn't care about something that small. But one of our previous Corvettes was supposed to have an automatic shutdown if the oil got down to 3 psi. If that feature is still on our 2009 LS3, then it might not work when needed and the engine could be destroyed unnecessarily.

Suggestions?

George's_Vette

Strange observation to catch that. Did you try cracking the oil filler cap to see if it released the pressure?

As for the 3 PSI shutdown feature I have no clue. Seems like a very low setting to try and save an engine from lack of oil circulation through the system.

George

EVRose

That does seem low. I'd want warning at probably 10 minimum.

Joe B.

My '91 had that. Pressure switch at the back of the motor. I believe it is there to prevent the engine from starting if there is no oil pressure.
Don't know if the C6 has anything similar.

2006c6keller

If the pressure gets that low and the engine is running, then I would be worried, BUT not running for several hours. The pressure probably came right back up when restarted. If ALL the clearances in the lube system are in very good shape (tight but in tolarances) that would not completely surprise me. In addition, what weight oil are you using AND what was the ambient temperature? I have a feeling you do not really have a problem.

You mentioned the "shutdown" feature, BUT that was with the engine RUNNING! You stated that you were not running. Therefore, that feature would not work even if it was on your car unless it was running!

Not all sensors, most likely in this case, a pressure/electrical conversion sensor is NOT perfectly calabrated as a "lab sensor" would be. You can bet that GM does NOT use precision Labatory sensors in this car! It would be too expensive, and the "bean counters" would eliminate it. I think this pretty well says it all.

I think you are probably all right!

FortMorganAl

I believe the C4 was the first to have a shutdown on low oil pressure. As I recall it was a separate switch from the oil pressure sensor. I would be surprised if there wasn't a low oil pressure shutdown today. On the other hand, as Keller alludes, 3 pounds is way too low for a reliable setting. That is barely outside the accuracy of these sensors.

I also wouldn't worry about it. You could check the wiring and/or replace the sensor but for this to be an real issue you would also have to have a major loss of running oil pressure which you have given no evidence to support. If it were reading 45 pounds when you knew you actually had 30 then I would fix it. But as long as the running reading is close to normal it only bothers you and not the engine.

Gearhead Jim

Since the engine had been shut down for several hours and was not restarted, pressure should have been 0.
Oil is Mobil1 5W-30, oil temp had probably cooled to around 120'F while shut down. Shouldn't make any difference after sitting that long.
The only reason I might care is if there is indeed a 3 psi automatic shutdown, not sure if the LS3 has that or not.

Anyone know about the possible shutdown feature?

cclive

The 3psi is simply the oil pressure sensor not being accurate. When mine went bad, at one point the gauge was pegged at 80 and the DIC said 121. To test if it was the sensor just reading high, I shut down the engine and put it in the 'ignition on' mode. Sure enough the gauge read almost 80 with the engine off. So the error of 80 plus the actual of 40 (which is normal) made up the DIC reading of 121. All yours means is that the sensor has a resting resistance that indicates 3 psi...when you run the engine, your indicated pressure will be the actual pressure plus the resting 3 psi error. As long as it doesn't get worse, it's no problem. If the error gets larger, like mine did, then it's time for a new $35 sensor.

Don-Vette

I agree with cclive, not very accurate....IMO nothing beats a mechanical gage.

HOXXOH

Not to worry. There is no method to retain residual oil pressure in the engine after shutdown. The 3 psi reading is either within the range of tolerance or the beginning stages of a malfunctioning sensor.

cclive

When the engine is shut down, the oil pressure drops to zero within a few seconds. It is then at zero by definition. Any variation as displayed by the DIC is simply a small error in the sensor.

Gearhead Jim

Everyone seems to be missing my question- does the LS3 have some kind of automatic shutdown when the oil pressure drops below a certain value?

Somewhere I saw in print that the LS1 in our 2001 did have an auto shutdown below 3 psi. If our LS3 has the same feature, and if it gets it's information from the same place as the DIC readout and the needle gauge, then the shutdown feature on our car is probably not working and I should try to get the sensor fixed.
But if there is no auto shutdown, or it's set at some higher number like 8 psi, then I don't care about the minor inaccuracy.

AORoads

No kidding, maybe a call/email to Chev Cust Svc to find out the answer to that valid question. If it existed in the C4 as Ft.Morgan states I can't think of a reason to drop it by the C6, but anything could happen. It also seems like some of the race shops would know since they put the stress to the engine far more than a street-only car.

cclive

With the number of bad oil pressure sensors, it may be a good thing that it doesn't have the shutdown feature. I would have been stuck in the middle of the Navajo reservation with a car that wouldn't run but had nothing significant wrong. Unless the engine has a second way of measuring oil pressure, I don't think there is a shutdown feature. Also, I've always thought of an oil pressure sensor as a foolproof item...the one on my Trans Am has been doing fine for 40 years now. Not so with the LS engine.

2006c6keller

Think about this! With GM's poor quality of parts, etc. as noted in the past, eg. harmonic balancer, clutch packs, shifters, rocker arms, iginitions, etc. Why would you rest your confidence that probably a POOR quality part or engineering would likely save your engine, etc., you are playing roulete, a risky solution! I think with GM history, ALL OF THE RECALLS, why do you think THAT GM WOULD HELP YOU or EVEN CARE ABOUT YOU? GM is a BAD DREAM!

HOXXOH

A quick test would be to disconnect the sensor wire and see if the engine starts. The gauge and the DIC should read 0, or in the case of your's 3. It's possible that the internal arm or the diaphragm has a bit of debris that doesn't allow it to completely reset, which means you won't see 0 again unless it dislodges itself.

Gearhead Jim

I suspect that IF the engine does have a Low Oil Pressure Shutdown, it must have some kind of delay when starting, if only a couple of seconds. Otherwise, we would need to get oil pressure before the engine could be started, or the engine would start and immediately die. The pressure comes up quickly, but not instantaneously.
Disconnecting the wire should allow the engine to start, run for a second or two, and then die.

I'll keep looking to see if I can learn more about this (possible) feature. When I can't find it in the poorly-organized Service Manual, does that mean it doesn't exist, or that it was accidentally omitted from the SM, or I'm just not looking in the right place?

Enquiring Minds Want to Know...

HOXXOH

I spent a couple hours looking in the SM for wiring questions a friend needed to know and kept an eye out for anything that related to the oil pressure sensor. What I found, was nothing we didn't already know. A google search brought up a video about sensor construction that was interesting, but also had no info about C6 sensors. I have the 2008 hard copy manuals. I assume the DVD version is the same, but possibly has a search feature.

2006c6keller

If anybody has a WIRING DIGRAM OR AN "AIRLINE" schematic, please locate the oil sensor and start traciing the wires back to each source and see where they go to AND beyond, they may take you on a GREAT CHASE, but may get you to a "shut down relay" etc. It should goto some circuit to shut the engine down, it might take alot of tracing to finally get to a shutoff relay, etc. IF there is one? You may find nothing, a real possibility! Therefore, the car does not have this feature or there is nothing connected for this feature!

Good luck!

HOXXOH

According to the wiring diagram in the service manual, the sensor wire goes to the ECM. Once it arrives there, it's not possible to trace the individual electrons on a piece of paper I can access.