B7 S4 Low oil light warning

[AvantNH]

2007 S4, 100k miles, no chain rattle (we understood we'd need to do them at some point)
Automatic
Purchased in August 2020
Carfax has record of lots of service, oil changes etc. No accidents.
Car is very clean.

The oil pressure warning light came on. Brought to local garage and asked them to change the pressure switch. The switch had oil in it so I figured that was the issue. The garage noted that the pigtail side of the switch wouldn't clip into the pressure clip so he added a little rtv to keep it in. The oil light came back on so I checked and the clip was not connected.

To be safe, we (my son and I) then checked the oil pressure at various rpms both cold and hot. Nothing registered low at either cold or hot temps and three different rpm spots.

We ordered a new pigtail, wired it in, put the clip back onto the pressure switch and let the car warm up.

No oil pressure warning light either cold or hot.

I put an OBDII reader on, no codes.

Reverse out of driveway, no light.
Move forward in drive and at about 10mph, light comes on.
Turn car off, back on, no light.
Rev engine, no light.
Put in drive, hit 10-20mph, light comes back on.

Still no codes thrown. (I was watching that as I was testing.)

My next step is to put the oil pressure gauge back in, duct tape it to the windshield, prop the hood so it doesn't bind, and check the pressure as I'm driving, but before that I thought I'd try to get some ideas from people who have experience with these engines.

Thanks!

[Racerx86]

There a ground wire that needs too b attached from the engine block to the sensor. Look up the sensor from ECS tuning an ull see the ground strap that comes with the sensor. If u dont want to buy a new sensor u can make you own ground. All u need is couple inches of wire any small guage will work an two ring terminals. Mount one too the bolt holding the crank sensor bracked an the other one can b put anywhere on the metal part of the sensor. Mine is ziptied too it just to where its pressed up against it an not loose. Hope this helps, good luck

[VinnysS4]

So was it a low oil light or an oil pressure light? 2 different things


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[AvantNH]

So was it a low oil light or an oil pressure light? 2 different things


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F me, yes, pressure. Edited the title.

- - - Updated - - -

There a ground wire that needs too b attached from the engine block to the sensor. Look up the sensor from ECS tuning an ull see the ground strap that comes with the sensor. If u dont want to buy a new sensor u can make you own ground. All u need is couple inches of wire any small guage will work an two ring terminals. Mount one too the bolt holding the crank sensor bracked an the other one can b put anywhere on the metal part of the sensor. Mine is ziptied too it just to where its pressed up against it an not loose. Hope this helps, good luck

I edited the post, it's the pressure not low oil... sorry! Thanks for the reply.

[roboto_1337]

If the mechanic has the original harness you can swap the harness on the new sensor so it’ll fit correctly. This needs to be done with some O2 sensors on our cars and the aftermarket clips are a different shape than the OEM ones.


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[x98boardwell]

What ever came of this? Was it the oil pressure switch?

[Matthewest91]

Most likely yes.
Or the wiring.

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[Rol-co]

Note:
Oil pressure warning will never come on at idle. Only while driving or above vcds adjusted rpm in neutral. Unplug the connector and drive, you'll see when.
Second warning it stays at the dis.

[Danisson]

Happened to my B6 a few times last summer when it was burning hot outside... check the level sensor down on the oil pan. It's basically an "electromagnet" as most of them and after all these years it starts to give signs of being at the end of its life. Basically its impedance changes with temperature so it gives a bad reading causing the "low oil" to show up on the dash.