Fixed.

 

p2647 lists for a rocker arm oil pressure switch, or, vtec oil pressure switch, so check the connections there and make sure everything is tight and if it's a new sensor maybe try swapping it out with another one, could be defective. (this is assuming, like you said, oil level is correct and you are using the correct oil)

 

Defective VTEC oil pressure switch, the wires going to it, or the ecu.

If you clear the code, can you drive around under 6k for 15 min or so and keep the CEL off?

 

Just to be clear...

Clear code, start car, let idle. Light comes back on then?