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DPF Light Flashing Engine light steady and code P242F - DPF filter restriction, Ash a

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DPF Light Flashing Engine light steady and code P242F - DPF filter restriction, Ash a

Old 09-03-2013, 03:37 PM
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Posts: 19
Question DPF Light Flashing Engine light steady and code P242F - DPF filter restriction, Ash a

Hi All,

In desperate need for help!

I have a 07 Mazda6 TS TD 143bhp.

The other day my DPF light and engine light illuminated out of the blue, on further inspection the oxygen sensor was reporting as defective with an open circuit heater. After a trial fitment of a new oxygen sensor I found that the original cabling had become defective, the new one didn’t work due to what appears to be a different heater element (double the resistance). So I refitted the original with new cabling which appeared to be successful, however, the lights remained on with a new code “P242F - DPF filter restriction, Ash accumulation”!

I have done some research which advises of performing a full regen, which nearly took an hour to complete, however, on completion I was unable to reset the DPF system using the methods described in Tips and Tricks for MAZDA 6 (GH) 2.0D MZR-CD (RF-Turbo) 2007 - 09. - www.cdn.dk.

I have an OBD II reader which clears the engine management codes but doesn’t clear the flashing DPF light!

Does anyone know of another method of resetting this event??

I’ve also noticed by monitoring engine stats that the boost pressure goes to 0 then drops and the engine changes note – this doesn’t sound normal but may be due to the fault recorded?

The car is currently in permanent Limp home mode

Thanks in advance!

Old 09-03-2013, 03:43 PM
Join Date: Dec 2011
Location: Canada
Posts: 2,636

Time for a new DPF! Mileage?
Old 09-03-2013, 04:02 PM
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Its done 147k and not sure of the history of the DPF?

Tomorrow I will attempt to swap the pipes (if possible) of the Differential Pressure Sensor to confirm a blockage. Not convinced it is blocked due to the fact it only reported after fitting that different oxygen sensor. hence my question about resetting the system. I may have introduced the event by changing parts?
Old 09-27-2013, 02:57 PM
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Join Date: Sep 2013
Posts: 6

Carl, did you get your problem fixed? I have exactly the same snag. CEL on with TCS and DPF flashing.

I tried changing the MAF sensor but no help. Car is kind of in a limp home mode but still cruises well. It is only when the engine is under load there is a lack of power and it is running very lean.

I have tried Wynn's DPF filter cleaner but after 1 tanks worth, so far no relief.

Does anyone know; is there a manual check you can do to see if the DPF is actually blocked?

I love my Mazda but am likely to go off it if I have to replace the DPF at only 69000 miles.
Old 09-28-2013, 03:58 AM
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Join Date: Aug 2011
Posts: 19

Hi Dolphin,

I should have updated my status but never got round to it!

I had the DPF removed completely (£300) and a software patch loaded to overcome the DPF control circuits and was also offered a upload of a Remap for an additional £100 – which is supposed to pay for itself by giving an additional 4-5 mpg and 35bph increase!

For me, the car has completely changed, improved response throughout the rev range and appears so far to be better on fuel an running as it was designed to!

I do recommend this to anyone where the control circuits have become defective or the DPF has become blocked as long as your engine is in good condition with no underlying problems.

Dolphin – In your case I would look at getting the ECU codes read via your OBD II socket which, will give diagnostic information and guidance to resolve the problem, please see link below for further information:
Codes and descriptions http://www.clearchain.com/~benjsc/do...789-1E-03G.pdf

My original defect was actually the four wire oxygen sensor had an open circuit heater which actually turned out to be a damaged cable, frustratingly after repairing the loom it then told me that the DPF was blocked which I was unable to reset
I did perform several tests that identified the issue with the aid of the document below (for facelift models):

Basically to check the DPF sensors, if you get under the car, you will have (if the same as mine) a row of four connectors, unplug each of the connectors, the four wire connector will be your oxygen sensor. The two wires the same colour on this connector will be your heater circuit and from memory should be 2ohms (or 4?) all the other connections will give a mV output but only whilst the engine is running.

I didn’t get round to checking the differential pressure sensors but was tempted to swap the hoses to fool the ECU.

Best of luck!

Old 09-29-2013, 10:46 AM
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Join Date: Sep 2013
Posts: 6

Thank you for the links to the documentation - very helpful. Pleased you got yours sorted via a dpf removal and remap. I am seriously thinking about it but not yet convinced I can't fix this a bit cheaper - money is tight!

Having read your post, I might now check the Hot O2 Sensor and the pressure differential sensor on the bulkhead in the engine bay before I do anything else. The only code mine posts through OBD II is P242F which according to the manual means a DPF blockage of 140% or more. I'd be surprised if mine was blocked that much - it has always been serviced at Mazda (last one only 5 weeks ago) so low ash oil used etc etc and most of my driving is on the motorway.

For anyone else out there reading this; after resetting the ECU, I get a solid DPF light, quickly followed by the flashing DPF light, then about 10 secs later the MIL and TCS come on with limp home mode. - you can hear a rise in engine tone when the MIL comes on.

I did get underneath the car and thought I would have a go at taking the DPF off and giving it a blast with a pressure washer but scared myself looking at all the air pressure sensors and electrical loom. (I had a diesel C5 where the pressure washer treatment worked a treat)

I did also try using mazda/tricks and tips (posted elsewhere) to force the car into a regen. It goes into regen but then the regen stops when the MIL light comes back on.

Thanks again for the info Carl. Not sure which way I'll turn yet. Long term relief looks like to take the route you have. Most of the quotes I have seen though have been nearer £500, including the remap.


Old 09-29-2013, 10:55 AM
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Hi Dolphin,

That's the code I had and couldn't reset it after fixing the actual problem

The price I paid was negotiated with cash which knocked £100 off.

I presume your from the UK, if so I had mine done in Sussex, if this is local to you send me a PM and I will give you the details.

Best of luck!

Old 11-13-2013, 04:19 PM
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Default help if possable

i have the same problem on my mazda 6 2007 this started when my injecter seals where leaking, the dpf light came on and it was regenarating , but then waiting for the parts the engine light came on and now its got both engine and dpf light on looked up the fault code p242f is coming up, any help will be very welcomed, i have had a oil change with engineflush and its still happening .
Old 11-14-2013, 04:08 AM
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Join Date: May 2012
Location: Queensland Australia
Posts: 3,462

Did the oil data get reset at the oil change?
Is the oil level at or below the Max mark on the dipstick?
I would avoid driving until the seals are replaced.
Old 11-14-2013, 05:35 PM
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Hi Dpf problems?! and grim reaper.

My car is still not fixed. (2007 MZR 143 BHP engine) In the end I took it back to Mazda. They forced it into regen and said it was fixed. I took it back 40 miles later with the DPF light flashing, the CEL on and this time P codes related to the MAF sensor. I already changed the MAF sensor so ruled that out.

They had it back in and told me I had bent a pin on the loom to the MAF sensor when I replaced it. The had also checked it for air/vacuum leaks. Gave me the car back and said it was fixed. 115 miles later the car went into limp home mode on a hill despite me having changed my driving style to drop into 5th gear every 50-60 miles and run it up to 2500-3000 revs for 10 mins as advised by the garage (to keep the dpf clear). Since then, the car has gone into limp home mode about six more times, normally on a hill with traffic behind me, after cruising/constant speed driving. It also intemittently runs rough (like missing) and is sometimes hesitant under light acceleration. Funny thing is though I get no warning lights...

The car is booked back in to Mazda again where I will ask them to remove and clean the Exhaust Gas Recirc (EGR) Valve. Why? Because there are other posts (look at the honest john one from 2008 by nitrox where with the same snag & they changed the ECU but no improvement) which seem to suggest that the EGR could be responsible...What makes mine more difficult to diagnose is that despite the limp home modes and rough running I have had no warning lights posted.

SO to the EGR. As I understand it, the EGR feeds exhaust gas back into the inlet manifold to cool the combustion process (Cool? I hear you say - I guess it is all relative) which results in less NO2 emissions and protects the engine from running at too high a temperature. At idle or under acceleration the EGR closes so that the engine breathes clean air but this raises the temp in the cylinders. When cruising the valve opens to provide the cooling action. If the EGR does not open when it is supposed too, the car goes into limp home mode to protect the engine from running too hot and producing too much nitrous oxide.

I had a go at it myself. After finally locating the EGR, I found it hard to get to the exhaust end of the valve to disconnect it, so I just took the metal pipe off that connects the EGR to the inlet manifold. Although it is about 20mm in diameter, mine was at least 50% clogged with soot. I cleaned out what I could with carb cleaner but cannot be sure the valve is not blocked from the exhaust end and therefore operating correctly. That was after about 3 tins of Wynns EGR cleaner so I don't reckon that is all it is cracked up to be!!

The problem continues to be massively frustrating because for the majority of the time, the car runs really well. There are sometimes though were I notice that I don't get the normal willing, bright response from the engine I am used to. There will be something in between limp home mode and "normal" The only other piece of imformation for anyone out there with similar snags is that mine is due a cambelt in about 4000 miles... Whilst it might be related, I'm thinking of not having the cambelt change done (expensive) until I have resolved the intemittent power problem. Chiken and Egg? Could a worn timing belt cause these snags??

We'll see how we go with the EGR and take it from there....Other things I have been told to consider are the Suction Control Valve and the ECU. I think i might have traded it in before getting to an ECU change.

What I find amazing is that there are so many stories of Mazda 6 diesels in various limp home mode sagas on the net, but Mazda do not seem to have collated enough data to be able to tell their dealers how to fix the snags which I'm sure are related. Whilst my car has generally been good, I think this version of the Mazda 6 has been a massive dent for Mazda's reliability reputation, because I think there is a fairly big underlying problem with this engine. otherwise, there would not be so many posts and the main dealers would have a diagnosis chart and solution be it a clogged DPF, injector seals gone, Suction valve, EGR clogged, MAF failed or faulty ECU.

Be nice if some from Mazda came up on this forum to put us all out of our misery....

Good luck with your car,


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