I just bought a golf a few days ago and noticed a light on it which i thought was the oil light as it is shaped like a tap (in my opinion anyway) and it says check. I was told not to worry about the light from the lady i bought it from that it stays on constantly but i am wondering will it fail the MOT for the light being on.

Iv looked in the manual and it says that this is the emissions warning light. It is staying on constantly and is a yellow colour. the car does seem fine, it starts perfectly and drives well and there is no weird noises, can anyone help me decipher what the problem would be or decide if the car will fail MOT for the light being on.