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A several days ago, I was driving up a fairly steep hill when my oil pressure light came on, and I got a warning on my car's display of low oil pressure. I stopped at the top of the hill and turned off the engine for a bit. When I restarted, there was no oil light. I checked the oil in case I had sprung a major leak, but the oil was full. From that point I drove down and back up that same hill, no issues. My car had been running for a good 20+ minutes, and I had driven it quite a bit earlier, so it was warm.

I never saw anything of that dreaded oil pressure light again until today. Once again the engine was warm. I had been driving for a couple hours. This time it was on a fairly flat road when it came on. I tried accelerating the engine in curiosity of whether the increased speed of the oil pump would affect it, and it did twice, but the light returned not long after I let off. After two tries of that, it just stayed on. At that point I was on a downhill slope, so I put it in neutral, turned it off, and restarted after a few seconds. The light never came on the rest of my trip home.

Being intermittent as it is, I feel (and hope) like it is most likely the oil pressure sensor/ sending unit. Otherwise my engine runs great. I have my regular oil changes and have had no engine problems. I've heard it's rare for the oil pump to go out on the 3800, and being it is not a constant issue, it leads me to believe it's not the pump.

Any ideas are appreciated!
 

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I'd check the wiring harness, first. The sender is buried on the back of the engine, above the oil filter, and wiring goes past the transmission and exhaust manifold. Also has knock sensor extension (clipped to the back of the PS pump reservoir), the Vehicle Speed Sensor (on the transmission tail cover), and possibly more as you try to get some length to work with (O2 on rear manifold, etc. don't remember exactly).

Sender replacement would be next, if the wires/connections look fine. If you were actually having issues with oil pressure, your engine wouldn't be long for this world.
 

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After you take a peek at the wiring, I'd replace the sensor. On the Series II the easiest way is to pull the passenger wheel and wheel well cover to get to it. Just unclip and pull off the connector then use a deep well socket. I use a 90 degree driver for my impact drill, piece of cake. The AC Delco version is only $18 but delivery from Amazon is really slow right now.

You might also need to verify on your engine if it's a 3-wire or 4-wire sensor possibly. Not sure on the Series III.
 

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A several days ago, I was driving up a fairly steep hill when my oil pressure light came on, and I got a warning on my car's display of low oil pressure. I stopped at the top of the hill and turned off the engine for a bit. When I restarted, there was no oil light. I checked the oil in case I had sprung a major leak, but the oil was full. From that point I drove down and back up that same hill, no issues. My car had been running for a good 20+ minutes, and I had driven it quite a bit earlier, so it was warm.

I never saw anything of that dreaded oil pressure light again until today. Once again the engine was warm. I had been driving for a couple hours. This time it was on a fairly flat road when it came on. I tried accelerating the engine in curiosity of whether the increased speed of the oil pump would affect it, and it did twice, but the light returned not long after I let off. After two tries of that, it just stayed on. At that point I was on a downhill slope, so I put it in neutral, turned it off, and restarted after a few seconds. The light never came on the rest of my trip home.

Being intermittent as it is, I feel (and hope) like it is most likely the oil pressure sensor/ sending unit. Otherwise my engine runs great. I have my regular oil changes and have had no engine problems. I've heard it's rare for the oil pump to go out on the 3800, and being it is not a constant issue, it leads me to believe it's not the pump.

Any ideas are appreciated!
A several days ago, I was driving up a fairly steep hill when my oil pressure light came on, and I got a warning on my car's display of low oil pressure. I stopped at the top of the hill and turned off the engine for a bit. When I restarted, there was no oil light. I checked the oil in case I had sprung a major leak, but the oil was full. From that point I drove down and back up that same hill, no issues. My car had been running for a good 20+ minutes, and I had driven it quite a bit earlier, so it was warm.

I never saw anything of that dreaded oil pressure light again until today. Once again the engine was warm. I had been driving for a couple hours. This time it was on a fairly flat road when it came on. I tried accelerating the engine in curiosity of whether the increased speed of the oil pump would affect it, and it did twice, but the light returned not long after I let off. After two tries of that, it just stayed on. At that point I was on a downhill slope, so I put it in neutral, turned it off, and restarted after a few seconds. The light never came on the rest of my trip home.

Being intermittent as it is, I feel (and hope) like it is most likely the oil pressure sensor/ sending unit. Otherwise my engine runs great. I have my regular oil changes and have had no engine problems. I've heard it's rare for the oil pump to go out on the 3800, and being it is not a constant issue, it leads me to believe it's not the pump.

Any ideas are appreciated!
I’ve replaced two oil sensors in the last year, first original one leaked bad, second one just when bad first then started leaking
 

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After you take a peek at the wiring, I'd replace the sensor. On the Series II the easiest way is to pull the passenger wheel and wheel well cover to get to it. Just unclip and pull off the connector then use a deep well socket. I use a 90 degree driver for my impact drill, piece of cake. The AC Delco version is only $18 but delivery from Amazon is really slow right now.

You might also need to verify on your engine if it's a 3-wire or 4-wire sensor possibly. Not sure on the Series III.
I agree , if you really had low oil pressure , you could very well hear tappets clicking of rod / crank knock . Most likely an electrical wiring problem or defective oil pressure sensor .

But , just to be sure , a long shot MIGHT be a defective oil filter . Cheap and easy to replace , then top off with the same oil you are using .

Best of luck to you , :)
God bless
Wyr
 

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If you think like a lot of us that it is not an oil pump failure. How about using a multimeter to test it. Test it before and after it is warm and then you can see if the voltage varies on the sending unit. As every here has advised you the wiring check would be so helpful. I had a 70's ford that had a rubbed wire that gave me a false low oil reading. If you are into tools and want to check the actual oil pressure Harbor Freight has a engine and transmission oil pressure tester for $40. In a few days between May 10th and 12th (one day only I can't remember which ) H Freight will have their 25% off coupon making it $30 + tax. It is a copy of an OTC unit that is $60. Then you could know what the pressure is while you find the short. Good luck.
 

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If you think like a lot of us that it is not an oil pump failure. How about using a multimeter to test it. Test it before and after it is warm and then you can see if the voltage varies on the sending unit. As every here has advised you the wiring check would be so helpful. I had a 70's ford that had a rubbed wire that gave me a false low oil reading. If you are into tools and want to check the actual oil pressure Harbor Freight has a engine and transmission oil pressure tester for $40. In a few days between May 10th and 12th (one day only I can't remember which ) H Freight will have their 25% off coupon making it $30 + tax. It is a copy of an OTC unit that is $60. Then you could know what the pressure is while you find the short. Good luck.
If the sensor is 2 wire , it may be a simple switch , set to open or close at a set pressure . If 3 wire , probably a sensor with the 3rd wire returning a signal ( as you described ) to the " computer " .

Wyr
God bless
 

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Discussion Starter #9
I figured I would update on this post.

When I looked at the oil pressure sensor, I found that there is a slow oil leak around it or nearby. The connection between the wiring harness and the sensor was soaked in oil. I assume this was making a poor connection, and was intermittently causing issues.

After cleaning the oil out of the connection, I haven't had a problem since. I may replace the sensor down the road for the sake of the leak, or if it starts becoming a regular issue. This ended up being an easy fix for now.

I'm very glad it wasn't truly an oil pressure issue... as we all know that would be a major ouchie...:LOL:

Thanks for all the suggestions!
 

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That happened to me last year. It was actually the sensor itself leaking into the connector. So unless you have a major leak from the valve cover or elsewhere above, there's a very good chance the sensor itself is causing the entire problem. For about 20 bucks and 30 minutes, I would replace it. And buy an OEM replacement.
 

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Guys im new to the forum looking to carry on this issue with mine. i have an 04 Impala SS. No oil pressure light, and gauge are bottomed out. ive replaced sending unit and traced wireing but still no fix. i have around 62 PSI oil pressure but the light and gauge are driving me nuts any suggestions would help.👀
 

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Sounds like something between the instrument cluster and the pcm signal. I think the sender reports to the pcm first, which runs the dash via serial data, if I'm remembering correctly.

Not a fun chase, regardless. Let us know how your troubleshooting goes.
 

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Well i know im not getting a signal to the sending unit, and i know it goes to the PCM ive traced all those wires. but im not sure of the pin out to the gauge cluster. i guess i need to pull the cluster and see the pin out there? IDK at this point🤯
 
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