Yellow Engine Management Light

[camcroft]

Hi. The yellow light keeps coming on and then when I do A long journey it goes off and then after a few days it comes back on I have tried doing a journey in a low gear ( 4th ) to try to burn off any build up but it doesn't seem to make the light go off. I only do short trips most of the time but the car doesn't seem to regenerate itself anymore as in when you stop and turn off the fan keeps going. I had some sensor fixed in the past that has to do with that could it have gone again or do you think it is a code that needs removing. Please help before I have to go to the VW dealer. Thanks in advance