a witness turns on

Friends of the Network, I have a problem with my car that is a Ford Focus TDCI 1.8 of 2005, a circle -shaped witness is lit as a pinion with a sign of admiration in the center. The engine works very well, the doubt is that I would like to know where the shots of the problem are going, I would like if some of you have any data or at least the workshop manual of this car model to know how to find the failure, I will be very grateful to you

In the manual that will have the car, or should have in the glove compartment, it will tell you that it is the light, with that to start it would be enough.