exhaust fault but what

[murtu]

when going to get the car renewal the was a fault with the exhaust

but i am not sure what is the issue as i didnt see any smoke coming from the car nor any visible signs of engine failure

so why did the wright that

[johnbimmer]

Its the level of HC (Hydro Carbon) they check, your must be old or high km engine, its quite common. If not then your engine must have been abused with late oil change many times to have high HC count.