2012 tiguan low oil pressure red warning light on and off once and awile.?

Ck the idot light (no offense) connection and wiring but first make sure you put enough oil back in. no offense again but you'd be surprised how many don't. You did everything else so if all that cks out probably time for a rebuild.

If you have been changing your oil and filter as suggested, go to your nearest Volkswagen Dealer and *ask them to plumb-in a mechanical oil pressure gauge to test your oil pressure at idle and 2,500 RPM. ** Did you change the oil pump pick-up screen in the bottom of the oil pan? Have you been using full synthetic oil which has stronger detergents to keep the inside of the motor cleaner?

either dirty oil or not enough oil or faulty oil pump or a pressure switch . at worse it could be your oil filter but oil must be pretty dirty .

another random part swap

first step check oil level on dip sticksecond step should have been to check all connections between the switch &  ECU

third step temporarily replace switch with pressure gauge & see that you do have adequate pressure even at idle when warm.

Oil pumps rarely wear out (unless run dry). Possibly air leak on suction side,otherwise worn bearings or leaky overpressure relief valve. Another possibility (rare) is aeration of the oil which can happen when the exit of the pressure relief valve is not smooth. Aerated oil doesn't pump well.

Let car sit for 4 hours at least(engine shut off) and then pull DIPSTICK & check oil level.  Where is the oil level ? it should be at least between the 2 lines or notches.  If the dipstick is dryish then you lack oil(you need oil to get oil pressure.)  That is the demand of EVERY ENGINE MADE by any company.  You don't wait to see the "idiot light"

. Then again, the car is 9 years old, so it has 90K miles on it so I would up the oil grade to 30W.  It is no longer new so there is slop between the parts. Excess slop allows the oil to leak out down the galley lines so squat is reaching the top of the engine and the sensor is at the top. Running dry is not what you want.

You need to get the oil pressure tested with a manual oil pressure gauge. It's possible that the bearings are worn which lowers the oil pressure. Have you been changing your oil nd filter every 3,000 miles or very 5,000 miles? If you've been going by the on board oil change reminder and not checking your oil level every 1,000 miles between oil changes there's a good chance you need a motor.

Have you actually checked the oil level regularly or ever changed the oil filter? We cannot assume that you have. 

(Change the oil and OIL FILTER.) What a dumb idea as that is not going to do anything for you. There is a reason the light is called a idiot light, they are not very dependable and will sometimes come on for no reason or sometimes will not even come on until to late. Make sure your oil is at the correct level is about all you can do. 

Change the oil and OIL FILTER.

How many people knows how, has the tools or even know where the oil pump is? If what you said is true then why are you here on YA asking as you know no one has the answer. You already know more than 99% of the people here on YA about cars. You should know an oil pump works or doesn't work so I don't know why you changed it. 

(Stupid thumb downers, you do NOT just change an oil pump, no simple job. The TD just shows how stupid you are.)