A challenging problem!

[haggettd]

DPF regen woes continue.
The story so far.
My car regens its DPF every 70miles.
All star diagnostics chek out ok apart from MAF which is slightly over reading.
DPF replaced (too full of Ash) under warranty.
No change to frequency of regen.
Changed Diff pressure sensor. No change to freqency of regens.

ECU is now main suspect. Can anyone think of any other thing that might be causing this to happen?
Why would the ECU call for a regen when it's getting all the right info and I know the DPF is clear?

Thanks,

 

[Alex Crow]

hello again, i doubt the ecu. wiring or software may be next port of call. also, have you checked with MB for any mods or known problems with relating to this issue? has the live data been checked on a road test? are any more faults being logged?

 

[MB Service Centre]

hi have had this a few times, first fix was software update, and 2 other cars i have had i changed the pipes that go onto the dpf sensor.
hope this helps

 

[whitenemesis]

Welcome to the fold Robert

Your experience in MB servicing will be very useful

 

[haggettd]

Thanks gents.
AP - No, the checks were all done in the garage, not on road test.
I haven't checked with MB specifically for mods and updates. Can a Main dealer service rep advise or would i have to go through MB customer services?
No faults are being logged at all - no codes left.

I had the ECU re-flashed after fitting the DPS. What does this actually do though? I might imagine that it means that the latest version of the software
with all updates and tweaks included. I might also imagine I'm completely wrong though:smile:

Thanks MB service for your advice, it's encouraging to know someone has come across this before.
Was the software update that you did do the same as my Re-flash or was it a specific patch that was designed to cure this problem. (I presume the problem was the same as mine and your update cured it).

Did replacing the pipes on the other two cars fix the problem of too frequent regeneration? If so, what was the problem with them? I understand that they are only pipes which connect the DPF to the DPS. They can only either work, get blocked or leak.

Welcome to the forum and many thanks for your interest.

 

[Alex Crow]

if you had the 're-flash' then yes, this is the software update for the latest version.

here is a theory, if the down stream hose had a slight leak in it, the dps could overead the dp value! certainly worth a very close look at the dps hoses. another thing to try is pulling both hoses off the dps and going for your long run. also worth getting it plugged in again to see when the last regen was, if it says 1,000 miles ago then think again...

 

[haggettd]

Well AP, believe it or not, I had the very same thought today re potential leaky downstream hose. Obviously it would show a bigger differential with higher rpm hence the sense in an on road test of said item.
There has however been a development! and an encouraging one at that.
When my new DPS was fitted and the ECU re-flashed, I reported that I had a regen shortly after. I had rigged a test thermocouple up the exhaust pipe and had a meter by my side so I could monitor the exhaust temp as I drove.
At a steady 70mph on cruise the temp read 170-180 deg C for 30 mins or so. Then the temp rose to 330-355 deg C and stayed up there for the 10 mins.
A regen it was then but the big difference was that the mpg figure did not drop as it usually does. Curious.
Went for another test drive today and the same thing happened again, ie big increase in temp but no apparent effect on the mpg.
I have optomistically concluded that the system may now be working as it should and is regenerating passively rather than actively (which is what gulps the fuel).

I hope that this is the case and is in line with its designed operation and not
just a false dawn. I'll have to monitor the mpg/temp over the next week and see what occurs.

As you say, the acid test will be to see when STAR reports the last regen event since I think it only reports active regens.

I'll pm you when I know more and in the meantime thanks so much for giving this problem so much of you thought.

This forum is invaluable because of the depth of knowledge freely given by those that know.

Cheers AP and all other contributors.

 

[haggettd]

P.S. AP I've just re-read your comment re plugging into STAR.
It was plugged in on Friday and the last regen was reported as 66km ago. This corresponded exactly to my last noted 'event' which was near Rugeley on Thursday night whilst driving home. Rugeley to home plus home to Balsall MB = 66km!