Motorcycle Questions? Ask a Mechanic.
Hi again and welcome back to the site, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.
Initially, let's try check/review the basics; have you checked and traced the yellow blue wire from the engine coolant temp sensor? ...cxheck fir nicks, rubbed raw insulation, or wire pinched?
And tested the continuity/resistance of the engine coolant temp sensor itself?
The simplest is it should not read 0 nor low and should be relatively high.
More particularly; a good ECT sensor would read 47.5 ~ 56.8 Ω @ 80°C / 80°C and 14.9 ~ 17.3 Ω @ 120°C / 248°C
Negative. The sensor only by itself even with the wire to it temporarily disconnected.
Yes, the sensor by itself. Its terminal (pin) resistance to body ground.
Other than the sensor, it is possible the yellow/blue wire as it may possibly be touching frame ground.
Another possibility if both the wire and sensor checks good would be a controller issue.