Thanks Railroad, some great advice there.

Now that it has happened in spite of my father's best efforts, what do you think my best plan of action is, assuming that I proceed with buying the car?

Should I just bite the bullet and buy a new one for £1,600 directly from Mazda, or is there a cheaper option available to me?

Thanks skidpan, that's really insightful. To be fair, my father took it to the local Mazda dealer the last time this happened (around a month ago), and they did connect it to their computer systems to do the necessary regen. This is what happened the first time too; I was just kind of explaining (poorly) what I thought the process consisted of.

It sounds as though my best option to really cure this, is to get a new DPF. Do you think I should opt for the £1,600 Mazda part or are the 3rd party DPFs just as good? I suppose there's a danger that the DPF sensors have melted onto the existing DPF, which could deepen the bill even more? I must admit that it's at this point I'm slightly out of my depth

Edited by steviebwoy on 01/09/2015 at 16:33

+1 to what the others said above. After 9 years and 110K miles, the DPF is likely to be fairly full with the ash residue from all the regenerations over its life, and will probably need replacing soon anyway (when the soot is burned off during a regen, it's mostly converted to carbon dioxide and water, but will always leave a tiny amount of ash that cannot be removed. Over several years and tens of thousands of miles, this eventually fills up the micropores in the DPF matrix).

My 10p worth is this: see if you can get a new DPF fitted cheaper. If you cannot get it cheaper than £1600, I would not buy the car ... bear in mind that other components such as the various DPF temperature and pressure sensors can and do fail too.

Thanks Craig, would the temperature and pressure sensors result in the same light combination appearing on the dash and the limp mode being activated? The reason I ask is because the fault has re-appeared really quickly after my father last had it regenned - probably around 100 miles. This makes me wonder whether it may be another fault contributing to the issue.

I have carried out a huge amount of DPF regens on these mazda's.

A you need dedicated diag equipment

B you must reset oil degredation counter

C you must reset injector learn

D I always reset EGR learn, ( if it smokes light blue during DPF regen the EGr valve is leaking and must be replaced )

E Clear any fault codes

F change oil and filter directly after

G I always reset throttle body adaption as well.

The engine will run at 1800rpm for up too 50 mins to regen and the DPF gets very hot, the bonnet must be left open, and do not move the vehicle whilst in regen mode.

as already said thrashing a diesel or driving too slow or too lower speed in too higher gear all adds to the soot content, including using full boost on acceleration.

With the exception of one Mazda 6 that had a blocked oil strainer and the engine seized I have never had one return with re-offending issue's once done properly.

The DPF can be removed and oven cleaned, these are the most effective way where they are baked in a DPf cleaning oven. ( Not home oven !)

Thanks, it sounds like you really know your stuff. Can I ask where you're based and how much you'd charge for this service?

Failing that, is my best bet to actually just get the DPF replaced by a local (non-Mazda) garage? I've no idea how much to expect to pay for having the DPF replaced, but it looks like I can source one from a local Motor Factors for around £400. Having it fitted appears to be cheaper than the component cost but I'd imagine, even with a new DPF, the vehicle will need retuning to recognise that a new part has been fitted. Is this something that a non-Mazda garage will be able to do for me?

Edited by steviebwoy on 04/09/2015 at 10:12