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Utterly strange oil sender unit issue

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2011 Chevy 1500 LT crew - 144k miles

So, after countless hours of searching, I’ve decided to post here in desperate need of help. 
My truck is currently in the shop, and on its 3rd mechanic trying to diagnose/fix the issue. 
Originally I was getting an oil pressure sensor unit code months ago, and about a month of driving later, and I finally lost my oil pressure gauge (dropped to zero) but the truck was perfectly fine. 
No loss of oil, etc. 

So I brought it in to get it fixed and change the oil - they put an OEM part in and changed the screen. 
Reset everything and I picked it up, a few moments later my check engine light returned. 
Scanned it when I got home, same error code - active. 
Checked for oil leaks, etc - nothing. 
Returned a month later for them to fix it, they put in another OEM part and new screen…drive it 3 miles down the road, and it trips again. 
They’ve checked the valve cover gasket and checked the PCM, everything seems fine. 
The truck is not burning oil either. 

I’ll add that my oil pressure gauge on my dash works fine now since they swapped sensors too. 

Everyone is stumped on what to do, and I’m about to potentially go down the rabbit hole of ‘throwing parts at it’. Starting with the PCM and then the valve cover gasket, and many thousands of bucks potentially. 

Does anyone have the slightest idea what’s going on? The PCM is throwing no other codes either, he has graphed and checked it. 
Is it possible for the PCM to be corrupt without it giving errors, etc? 

The tech is a 30 year vet, and a family friend - so by no means is he stupid. But this has stumped two other techs with equal experience too. 

Now my truck is past inspection, and with my Check Engine light on, it’ll never pass. Plus I’m still half way on my loan, so just selling it isn’t an option. 

Edited by Eastcoasteric
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ask a friend or your mech if you can swap out the pcm with another truck see if it clears.  I wouldnt think that check engine light would fail you. I thought only emissions would do that.

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BEFORE I did anything else I would get that sending unit out myself and see if there is foreign crap inside the sending unit's little bore. It's not easy to get to but it can be done, it's in the back of the engine just about where the distributor would be on a small black. It's HARD to see without a mirror. If there's crap in the bore I'd get some BG engine flush. Not sure that's the product's proper name; you can usually get it at NAPA, maybe Autozone...others. Bearing and Gear make some pretty good "mechanic in a can" type products. Wen I was on Active Duty they came out to the shop and demonstrated the product line. I was very impressed. Anyway after you flush that engine I'd try another sending unit. You could put a T under that unit, run a copper line to a good old fashioned oil pressure gauge and mount it under the dash for your own information..

I mean it's POSSIBLE you could have enough crud in the motor to disable the sending unit; flourishing the crud out would eliminate that POSSIBILITY. After the, I'd be looking for some one that could BENCH test that PCM for proper operation.

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