What does an anti-pollution warning light on my 2004 Citroen C5 suggest?

I've just acquired a 2004 Citroen C5 saloon that's done 100,000 miles. I've been driving it for a few weeks now and have an anti-pollution warning light on the dash. Is this serious? There is some service history on it but stopped in 2011.
Yes. Serious. The C5 was one of the first diesels with diesel particulate filters that were designed to last about 60,000 miles and also employed a reservoir of Eolys fluid to regenerate them. It could be you are out of Eolys, or the system isn't working, or the DPF is choked with ash.
Answered by Honest John on

Ask Honest John