Yeah, it's the oil pressure switch. I had the exact same thing in the winter. It starts off by coming on at idle and going out again when you blip it, but after a while it'll start to get worse. Mine started flickering and then staying on solidly about 5-6miles into each ride. Since I knew I had enough oil, and knowing that if the oil pressure had been low it would've started to make expensive grinding noises after a few miles, I did a couple of hundred miles on it before Nelly replaced it at service time.
Jools
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