my diesel car’s emissions control device is blocked, so who is liable?

If your car has developed a fault, or for consumer advice, turn to Honest John by emailing honestadvice@telegraph.co.uk

Soot alors!

I bought a 2016, 28,000-mile Mazda CX-3 1.5 Skyactiv D three months ago. I frequently do 40- to 50-mile round trips on dual carriageways and motorways. The diesel particulate filter (DPF) warning light is now flashing. I took it to an independent garage for a full service, including oil, air and fuel filters. The mechanic plugged it into the diagnostic computer and several fault codes came up, including DPF soot and ash blockage. I have a six-month warranty that covers the DPF, but not if it is blocked with soot or ash. Should I take this up with the selling garage? Or should I take it to a Mazda dealer, get a diagnostic report and see if Mazda will make a contribution towards the costs, which will be substantial? KW

That should be sufficient mileage to preclude issues with the emissions equipment, so it is likely that the DPF was almost blocked when you bought the car. The selling dealer is liable for any fault that could have been present or developing on date of sale for six months from date of sale. A warranty cannot cover a pre-existing fault. Send a letter to the dealer stating that, for this particular fault to have developed, then the soot and ash in the DPF must have been building up on date of sale and you hold him responsible for fixing it. The law on the 1994 Sale and Supply of Goods Act is Clegg v Olle Andersson (trading as Nordic Marine), House of Lords, 2003. Send your letter by Royal Mail Special Delivery, keep a copy and the certificate of posting, use the reference code to check it was delivered and print out the certificate of delivery, then staple them all together in case you need them in the future to prove you attempted to resolve the matter without going to law. 

Heavy mettle

Is there a used, 2.0-litre turbodiesel that is reliable, relatively economical, capable of towing a 1,500kg caravan comfortably and, if treated properly, less likely than the competition to present problems with its diesel particulate filter (DPF) and associated emissions gubbins? JB