[Benedict]

P243C,means it is regening too frequently, younwill also find that your sump level has increased and could well be over the Full mark.
With 80K you have done well from new but you need new injectors.
You could try proving the pipes to the DPF dp sendor and the N0.1 Exh pressure sensor are not blocked, by removing them from the rubber pipes , have an assistant rev the engine and you make sure all three pipes blow freely. The highest pressure is the single (No.1) the lowest pressure is one of the DPF hoses, which is After the DPF.
If all those blow clear then its could well be the injectors. Also check your MAP sensor is clean of carbon.
Injectors are about £500 each, none Mazda, fitting is about an hours labour.

I went through that back at 45k and the Service Manager hadn't a clue, it wasn't in the fault fiinding, he changed the DPF dp sensor twice and it still came up, called Mazda in Kent. 'Oh! yes we know all about that problem, it needs new injectors'. What they don't admit to is its a manufacturing defect that they kept quiet about. Its due to cavitation erosion or the injector nozzle holes. Same thing happens on ship and boat propellors with bubbles imploding and causing erosion of the metal. In Mazdas case the nozzles are not hard enough. Firing pressure is in the region of 2000bar. So you can see there is a lot of energy there to do damage if the nozzles are not hard enough.

The attached is for any 2.2d engine, Denso supply the injectors, plus other stuff.

New injector

Worn injector.

The nozzle holes are larger and ragged, this produces poor spray pattern, incomplete combustion, excessive carbon build up in DPF and frequent regens resulting in P243C code appearing.
Eventually the the regen frequency gets down to 30 miles, yet the car runs fine. I was doing 50 mile round trips just after Covid with the light permantly on, even hit 90 mph for a very short test, though if left too long the holes will enlarge to an extent that the nozzle end could drop off.
Some places will say, you need a ultrasonic dpf clean or a new one, it won't make a h'apporth of difference. The DPF and the regening is working, you have to deal with whats causing the higher frequency. Treat the cause, not the effect.
Good luck.

 

[Benedict]

Cam4zero, no you cannot have it removed the MOT would puck it up straight away, you would also get a lot more codes come up. Don't even think about it.
Take the sensors off the exh pressure pipes and prove they are clear by running the engine and have somebody raise the revs and check if they are discharging, watch the single one , it will be hot.
You can see the sensors here, there is a 2 & 1, prove they are clear.

These engines don't like town or short runs, but often its the way your life is.
The petrol it would appear is a dream, no inherent problems, but finding one thats not been abused.
Keep in touch.

 

[Benedict]

Yes thats correct about the Differential Pressure sensor pipes.
If you remove them at a time when you will not be using the car afterwards and can leave it overnight, pour some washing up liquid and a small amount of water down each pipe.
I use a silicon tube nozzle as a funnel. Soap disolves carbon if left for for a period of time.
If the tubes prove clear and the sensors are woking then its the injectors.
Mazda dealers can buy aftermarket injectors at half the price of Mazda ones, the difference is a 1 year warranty rather than a two year warranty and price gouging by Mazda. They are both made by Denso will last the same amount of time before they are worn out.
There is not much in the diagnosis that Mazda can do.
Idealy the injectors should be removed and tested in a machine, but dealers don't have these machines, only Fuel Injector specialists like BOSCH have them.
One test they can do with a simple kit is a leak off test, which measures the leak off of fuel whilst the engine is running.
If the leak off is the same across all cylinders they are working ok, but if there are discrepancies particularly low amounts it means those injectors are worn allowing more fuel through. If the level is high it means the injector is stuck.

 

[Benedict]

How is the oil level, if its rising then a good chance its the injectors.
You will note the single exh pressure sensor is on a banjo, this sometimes gets blocked, hence the test of making sure they all blow free. To remove the banjo a banjo bolt is a very awkward job, hence using washing up liquid to disolve the carbon.
Use of Forscan software and an OBD11 dongle is handy if you know what you are looking for in the data.

 

[Benedict]

Mickyc,
I don't think there is a normal distance between regens, but when the injectors are new and you are on a long steady run at 130 kms/hr then it would be close to 320 kms, but as the injectors wear ( and they do, due to cavitation erosion of the nozzles) then that distance starts to drop and more quickly if you are doing a lot of town driving as most of us do.
That's a good distance you have on your car, are you showing any codes?
When the regen frequency gets down to low double figures, you are going to see P243C, which means too frequent regens and you will probably need new injectors.
There are a lot of myths ( not Irish ones either) by none Mazda mechanics that think that DPF's need an internal clean, yet according to my last Mazda Service Manager, they don't need off car cleaning unless they have been burning a lot of oil. He said he only changed one in 12 years and that was due to failed seals in the turbo.
As you are keeping a check on frequency of regens, also keep a check on fuel consumption by calculation, this will also start to drop over time.
I have my fuel consumption on Excel from 2014 when I bought the car.
Also log oil dilution, this is also an indicator of the injectors failing and sump level rising.
If you are thinking of keeping your car, I would start to save up for some injectors, cleaning & fitting time is about 1 hour, but the parts are quite expensive, though if you have the Denso ones rather than Mazda ( exactly the same injector as Denso make them) you get 1 year warranty, rather than 2, and depending on your yearly mileage they are going to fail well beyond the Mazda warranty anyway. If they fail within the Mazda warranty period , Mazda will say you are not driving the car correctly and get out of paying which is a lot of nonsense. There is nothing in the handbook on how you should drive it.
So it would seem these days injectors are a service part due to Mazda/Denso getting the design/heat treatment wrong, or on purpose due to banning diesel cars off the road.

I was looking at a Toyota Corolla, but they are all automatics and hybrids, so I will hang onto my M6 a bit longer.
If they want an efficient car with low emissions, why fit an autobox and lug around extra batteries , propulsion motors and control gear increasing the weight, wasting fuel on charging the propulsion battery for what range and what savings on emissions. I think the emissions quoted were very close to the M6 2.2d when new.

 

[Benedict]

Mickyc, Miles/Km on a full tank is not really the best way to measure fuel consumption, nor is it good practice to run it down so low. Fill up at 1/4 tank and calculate mpg.
An easy way to clear the pressure sensor pipes is to remove the sensors, and run the engine to see whats blocked, then run washing up liquid down the pipe and some water. Soap disolves carbon.
Cleaning the pressure pipes won't prevent the MAP being covered in carbon. Thats due to the use of the EGR, and town running. You have no control of EGR use.