Check witness on Daewwo Nubira

Greetings to all before starting, because I am a rookie in this forum.
I have a 2003 Daewoo II with 26,000 km. Suddenly and without noticing anything in the vehicle, the Yellow Check witness of the light panel has been lit. The light is fixed and does not disappear.
Although I know that I have to go to the workshop, but since I have a bad experience with another vehicle from another brand that tried to change pieces that were not, my question is as follows:
What does this witness indicate if the vehicle works apparently well? Can it be a sensor that does not work well, and if so? Can I rule out the catalyst as the cause of the fault?
Thanks in advance for help and greetings

Look with respect to the witness light, any signal to the dough can be produced and that is why it is turned on without the engine already fails, the other k the non -diagnostic tety

To a colleague friend, something similar happened to a Corsa, and went crazy with the Scaner since he indicated different elements every time he replaced one.
The problem was a sensor (I think of temperature) simply disconnected.

JUAN

Hello, check light in the cohes turns on when the motor control unit detects a malfunction of electronic management. In your particular case if you notice that the car works normal, it may be that at some point the reading of any of the injection system sensors detected an unusual parameter and therefore that fault caused that the check light is turned on Wiring A detail, in the cars at least 50% of the faults are caused by the wiring to be determined or by false contacts is not always the damaged sensor. On the other hand you must make an electronic diagnosis of the car in some carver that has the tools (scanners) suitable for your car.

Thank you very much for the information. I will see if I locate a trusted workshop that has the notagical dias. In principle distrust of the official service for a bad experience.