dashboard warning light

[normal bloke]

I have had a light permanently lit on my 2004 Golf TDI for over 50000 miles. My garage who services it every year says it's nothing to worry about and it always passes it's emission test for the MoT.
According to the manual it is showing an "exhaust system fault". Delving further into the manual it says, drive-slowly-to-your-nearest-dealer-before-you-destroy-your-engine-sort-of-thing. I honestly don't worry about it but what happens when I try to sell the car? It's unlikely that I'll be able to persuade a perfect stranger that there's nothing to worry about. will I?

[Dr G]

Said stranger will be concerned about it and as of this year warning lights are MOT items too.

[normal bloke]

Yes, it's obvious really. I will attend to it in due course.