My 2009 IS 250 has an issue that right turning indicator will stay on/flash when I turn on. It will become darker but still on after a while of driving. Anyone experienced this issue before and knew how to fix it?

 

Is the indicator only on the dash, or is it on the head light too? I think 11-13 models only have one bulb. 06-10 have two. Can you see if the headlights have condensation maybe water in that area of the turn signal bulb?

 

FWIW 11 - 13 front turn indicators are amber incandescent wedge bulbs. Marker lights and swoosh are LED on HID cars.
Halogen low beams use 5W bulb for marker lights.

Rear turn indicators also use an incandescent wedge bulb.

OP, check your lights. A bulb out can make the dash indicator glow. Also check for strange behavior witht the lights on. A bad ground could be a possibility too.

 

Or dirty relay making poor contact? Maybe the CF18 relay is not functioning right or is dirty?