Light critical temperature flashing Passat TDI 96

hello friends.
I have a problem with the temperature witness and I don't know where to continue.
I changed the bulb of injection and it is not, I don't know where to keep looking.
If someone has an idea where the signal of that witness comes from makes me a great favor.
I have been solving this for a long time and I can't solve it.
Thanks for the help
greetings.