Car failed mot - emissions

[Pollqueen]

Hi, can anyone advise please. My Citroen D5 has just failed its MOT due to excess emissions. However, garage says they can't establish what the problem is to fix because their computer is unable to read my car, despite same garage doing the last 2 MOT'S on the same car

I asked where I go from here and he just shrugged his shoulders and said maybe a different garage could help. Has anyone experienced similar or able to advise?

Is it a diesel? Good blast down the motorway drive it at higher revs than normal. And take it for a retest whilst it is hot

Hi Scully and thanks for responding. No, petrol

They mean their diagnostic equipment can’t read it not the MOT emissions equipment. The oldest trick is to give it a proper hammering and get the cat red hot then straight onto the emissions test. It could be anything though really from a fucked cat to an exhaust leak to an oxygen sensor. I’m surprised they didn’t give you some insight based on the actual figures it’s producing.