chevy venture 3.4L confusion

I have an issue with a chevy venture with a 3.4L engine with 144000 miles.
Light came on after an oil change after warming it up.
Dealer checked it, said 0 PSI at idle.
Car sat for a month.
Changed oil with Lucas after a recommendation.
Light still came on after warming up.
Ran car and raced the accelerator having a gear head friend listening, no noises.
Changed pressure switch.
Got car washed, which was done after the above 2 oil changes. When turning the wheel with the car in gear, light started BARELY flickering.
Drove the car to the same gearhead, listened and raced the engine, no bearing noises.
No light since.
Have not lost any oil or antifreeze (manifold gaskets were changed at 135000 with GOOD gaskets).
First dealer said they tapped into the block to check pressure, bypassing the pressure switch when they stated 0 PSI.
Questions - did Lucas fix it, or was it the switch, or did the Dealer lie and not check it?
No overheats, no loss of oil, no noise.
Confused - Ideas? thanks in advance!!!!
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Walt wrote:

Go get a mechanical oil pressure gauge and connect it up yourself. Then see what you actually have. Until you actually see what you have it's all a guess.
--
Steve W.

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Is there indeed another port in the block for checking oil pressure, or is it just the pressure switch location? The dealer told me I have a transducer and not a switch, but all schematics indicate an on/off switch, which grounds out to turn the light on with low oil pressure.
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Walt wrote:

Just unscrew the "transducer" (You are correct in that the one for the idiot light is a simple switch) Screw in the hose fitting for the pressure gauge and see what you have. It could be that the pump is starting to fail but is pushing some oil. Or it could be that the oil passage to the sender is plugged with crud or the wiring has a problem.
Without actually testing the actual pressure you can't know. You don't need anything fancy just a pressure gauge that you can read and a way to connect it to the engine.
--
Steve W.

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I am planning on borrowing/using a pressure tester. I have no noises from the engine, but I was told by the dealer who tested it: 1. They hooked it up to another port to eliminate the possibility of a bad sending unit. Is there any port in the block, or just the one? 2. That I have no oil pressure. Possibly bad cam bearings which are the first to go. Even though I have no noise (not even valve ticking) I could have bad oil pressure. When I told him the light doesn't come on he said "good, but you still have no oil pressure".
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there are a couple, BUT I like to use the one that is involved with the problem.

No oil pressure, not really possible without noises.
--
Steve W.

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Where are the others? I'm thinking I have a crud problem, or electrical (hence the car wash). But why the dealer said 0 PSI and I have no noises (or loss of power) I don't know.
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Not sure about the venture but my cavaliers had two oil pressure sensors. One was to the idiot light. The other was a switch that shut down the fuel pump with low/no oil pressure. I gave away my service manual with the venture....
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