Hi Georgina,

I'm assuming you mean the exhaust filter warning light for the diesel particulate filter (DPF).

Whether you can fix the problem without changing the filter will depend entirely on what make and model you have and how clogged the filter is. First thing to do, assuming the car isn't in 'limp home' mode where it won't deliver full power, is take it for a long motorway run where you're able to go consistently at the speed limit or thereabouts for about half an hour. Choose a lower gear than you would normally for this so the engine is running faster (and louder - it won't be pleasant) as this increases the exhaust gas temperature and helps to burn off desposits that are clogging up the filter.

That may be enough to remove the problem, but even if it does, in some cars it'll still be necessary to have the light reset using a diagnostic computer in a garage.

You can also get additives from motor factors to put into the fuel tank that might help clear the problem.

If none of that works then you need to bring the car to a good garage to look at your options. You can replace the DPF fully, which is very expensive, or sometimes have it removed and professionally cleaned out.

Best of luck