I was getting this error right when outside temp was getting above 0. I was driving slowly with second gear mostly then it was hitting first time. Engine start running roughly and and error was flashing in dashboard. Well stopped bike and started again and it was working ok. Next trip it was happening once again while I was driving slowly. I restarted bike again and it was working again end of the trip. Last week I was checking some new slow trails and issue was hitting again it happened several times in that trip so I decided to give some proper look what is going on.
I found from google other people that had has same issues and they have took bike to repair shop but it has been tricky to find issue even there. Finally they were finding out that issue is in voltage regulator that might start failing when bike gets hot.
Here are couple videos where error is on and you can hear how engine sounds.
So fix would be getting new voltage regulator and preferable MOSFET one. There were recommends to buy fh008 type or FH020 MOSFET R/R. In these you need to modify cables to get those fit to bike. While googling different options I found Carmo electronics CARR694-KTM 690 950 990 MOSFET Voltage regulator rectifier. It is plug & play solution and no need to modify any cables.
Below some images about change process.
There are 3 wires that are connected to regulator. Ground then one with white connector and then one with brown connector other side of bike. Taking ground and separate white connector were easy, but brown connector was bit more tricky as there was some dust and dirt inside it.
I pushed small flat screwdriver to get that little notch down and then connector was released successfully.
As left side cable goes behind radiator, I released it from up and removed front fender. This gives enough room to release old cable.
After cables are released we can remove old regulator from frame and install new one in place.
After everything is back in place we are ready to hit road again.