P0101 MAF and P2463 DPF soot problems...

[Problems]

Hi, I’ve spent 2 days testing and searching on the web and haven’t been able to find an answer and I’m hoping someone here may be able to point me in the right direction – I’ve signed up specially!

I have the below 2 fault codes on a 2011 W204 C220 BlueEfficiency CDI on 165k

P0101 - Mass or Volume Air Flow Circuit Range/Performance Problem

P2463 - Diesel Particulate Filter Restriction Soot Accumulation

About 1.5 years ago I had the engine light come on and into limp mode, I read the fault code and it was the Diesel Particulate Filter Differential Pressure Sensor. I bought a new sensor from the dealer for £60, fitted it, reset the code and the car came out of limp and was fine.

This time driving along under heavy load (accelerating on dual carriageway after roundabout) I felt a loss of power which was the car going into limp mode (3k rpm limt). No engine light straight away, but that came on the next time I started the car. Unfortunately I had to drive it for another 350 miles / 15 hours before I could read the code. When I did, I got the P0101 and P2463 codes.

I’ve checked around the MAF sensor and no obvious signs of split hoses. The air filter is recent and looking at the ‘live’ OBDC2 data, it shows the MAF as 1.7 lb/min at idle which goes up to around 14 lb/min when driving (in limp mode). Does anyone know what normal figures would be for this engine please?

I removed the MAF sensor, it looked clean but I gave it a clean with carb cleaner and then isopropyl alcohol plus contact cleaner on the electrical plug. Retested and live figures were just as before.

If I clear the fault codes, they disappear, but both come back as ‘pending’ faults as soon as the engine is started. After a journey or two, both codes become ‘real’ codes and the light comes back on. The codes always show as a pair.

The MAF sensor appears to be sending values back to the ECU, but the car stays in limp mode even after a reset. I’m concerned that it’s not regenerating with this fault and limp mode on, so the filter is blocking up – hence the second code.

Has anyone experienced something like this? Is there a MAF problem that has caused no regens and hence the filter is blocking, or does a partially blocked DPF cause a MAF issue? For some reason this particular MAF sensor (part no 6510900148) is more expensive than others at £250+ so I’m reluctant to replace it when the existing one could be ok? Any help very gratefully received!

 

[Problems]

Hi, would this be better in the Electronics section?

 

[wu56Shoozz]

Don't panic the board is always a little slow to respond, so be patient.. I'm sorry I can't help you other than that..I don't think your problems are related but more the MAF is coincidental.. how much is a new MAF? have you tried getting a good secondhand one and trying that? (Not sure if it needs coded or not) other than that I don't know what to suggest...

 

[m80]

I have similar with my Viano, but not the same. I'm not getting DPF codes just the same MAF code.
Even when I get to the bottom of my issue I'm not sure it will help with yours.

After resetting the codes I'm getting the MAF code 'pending' back even before I start the engine, are you?
Can your diagnostic kit read the soot content level?

To my mind the MAF is a sensitive sensor and it maybe that cleaning it as you have isn't good for it, maybe others will comment on that.

 

[Problems]

Hi, thanks for the reply. Yes both codes come back as pending as soon as I start the car after clearing the codes, then after a day or so the light is back on and the codes are back.

I’ve only got a basic OBD2 tool so can’t read the soot content. I don’t know if the soot code happened first, or if the soot has built up as I don’t think it will regen the DPF with the MAF fault present.

Is yours also in limp mode?

I’ve found a MAF sensor from a company in Germany at a better price, so have ordered one last week, tracking info shows it’s on its way…

 

[m80]

Mine feels like limp but revs to max and kicks down so not. I believe there is no turbo boost

With mine bringing up the MAF code before starting the engine I'm able to see that, to my mind anyway, it's a sensor or ECU fault.

I have been using the iCarsoft V2 till it also went faulty yesterday. That has shown me that the map boost sensor didn't change state while driving so I've ordered one.
It can show DPF differential pressure, exhaust back pressure and soot content.

I replaced my MAF last week and no difference
I believe cheaper non oem MAFs are suspect and can be problematic themselves, I went for Bosch.

 

[HITECH]

Revs up to full but power loss. Yes that will be your exhaust back pressure sensor for sure. How sure am I . Well the components that cause that specific fault are very limited and the most common one is the exhaust back pressure sensor. Top right of your engine beside the EGR. I already am advising somebody else on the forum for a limp mode of similar nature. You gone about it the right way, DPF sensor then ...... Replacing your exhaust back pressure sensor and cleaning out your EGR and all the routes/lines full of soot shoudl cure it.

Mine feels like limp but revs to max and kicks down so not. I believe there is no turbo boost

With mine bringing up the MAF code before starting the engine I'm able to see that, to my mind anyway, it's a sensor or ECU fault.

I have been using the iCarsoft V2 till it also went faulty yesterday. That has shown me that the map boost sensor didn't change state while driving so I've ordered one.
It can show DPF differential pressure, exhaust back pressure and soot content.

I replaced my MAF last week and no difference
I believe cheaper non oem MAFs are suspect and can be problematic themselves, I went for Bosch.

 

[m80]

Thanks HITECH, I see a danger here of my hijacking this thread so I've started another,
Create Thread | MBClub UK - Bringing together Mercedes Enthusiasts

 

[Problems]

Hi, no problem. m80 has the same P0101 code as me so it may be related?

When you say the exhaust back pressure sensor, are you talking about the DPF differential pressure sensor? I had that error about 1.5 years ago, but the error was that specific sensor (not a MAF error), I replaced the DPF differential pressure sensor for £60 and the fault went away – after resetting the codes.

 

[HITECH]

DPFE sensor, Exhaust back pressure sensor and O2 sensor are 3 completely diffirent things. some mechanics ive come across have put their hands up to not seen too much exhaust back pressure sensors. So when u talk to them they assume its o2 sensor or dpf sensor. Its neither of them. the o2 sensors are plugged into the before and after cat, the dpfe sensor is plugged into the dpf via 2 hoses. The exhaust back pressure sensor is screwed into the same line as the EGR valve so it is monitoring the BACK pressure. Here is a link to an example of what it is>>>>>>

Genuine Mercedes-benz Om642 Engine Exhaust Back Pressure Sensor A0091535028 | eBay

Hi, no problem. m80 has the same P0101 code as me so it may be related?

When you say the exhaust back pressure sensor, are you talking about the DPF differential pressure sensor? I had that error about 1.5 years ago, but the error was that specific sensor (not a MAF error), I replaced the DPF differential pressure sensor for £60 and the fault went away – after resetting the codes.

 

[m80]

Hi, no problem. m80 has the same P0101 code as me so it may be related?

When you say the exhaust back pressure sensor, are you talking about the DPF differential pressure sensor? I had that error about 1.5 years ago, but the error was that specific sensor (not a MAF error), I replaced the DPF differential pressure sensor for £60 and the fault went away – after resetting the codes.

Yours being a running fault and mine being a static fault the symptoms are a little different so I'm expecting the resolution to be different. The diagnosis for mine might end up leading someone with your symptoms down the wrong route for them.

 

[HITECH]

Have any of you guys actually ran your cars with the MAF unplugged ? It will throw up another 2 codes but this should be the first and foremost test to do with a limp mode fault and a MAF error code present. Both of you do this for a few hours/day driving and report back. How does the car drive with it unplugged ? Ignore the 2 errors it kicks up and also ignore the engine light that comes on (if it aint already on). How is the car performance then.......... report back.

 

[m80]

Aye, I ran but just for a few miles,
with mine both MAF's run the same, plugged or unplugged it runs the same.

What does that tell us?

 

[HITECH]

Try for few hours or half a day. Not a few miles. It will not do any harm running it like that. For one. U can stop looking at your MAF as the fault.

Aye, I ran but just for a few miles,
with mine both MAF's run the same, plugged or unplugged it runs the same.

What does that tell us?

 

[Problems]

Have any of you guys actually ran your cars with the MAF unplugged ? It will throw up another 2 codes but this should be the first and foremost test to do with a limp mode fault and a MAF error code present. Both of you do this for a few hours/day driving and report back. How does the car drive with it unplugged ? Ignore the 2 errors it kicks up and also ignore the engine light that comes on (if it aint already on). How is the car performance then.......... report back.

Thanks for the replies, unplugging the MAF gave me 2 new codes, 'MAF input high' and 'air temp sensor input high' which I guess are the 2 codes you are referring to. Car seems to drive ok without the MAF, but I haven't driven it far yet.

My new MAF sensor arrived from Germany, I fitted it and... nothing. Well, exactly the same as before:

P0101 - Mass or Volume Air Flow Circuit Range/Performance Problem
P2463 - Diesel Particulate Filter Restriction Soot Accumulation

Live data figures for the MAF whilst driving were pretty much the same as before, so either this new MAF is faulty (unlikely) or my previous one is ok.

 

[Problems]

I’ve been looking at the live OBD2 data and the Absolute Throttle Position is always 87.8% and the Relative Throttle Position is always 100%, but I assume these are fixed as this is a diesel so it doesn’t have a throttle controlling air into the engine as a petrol does, is that correct??

There are two Accelerator Pedal Position values which go between 5.9% and about 93% which I assume is normal.

This is a stock picture, but I have circled the MAF in green, the MAP sensor in blue however there is something with a 2 pin connector attached to the intake pipe below the MAF unit, shown in red. Does anyone know what this is please? When I disconnect the other sensors, I get errors, however when I disconnect this 2 pin connector I don’t see any errors come up, is that normal?

 

[Problems]

Just in case it helps anyone else, Green circled sensor = Mass Air Flow (MAF), blue circled sensor = Manifold Absolute Pressure (MAP) and the red device is a crankcase breather heater.

 

[HITECH]

If your new MAF sensor is of decent quality then u can safely say that a MAF problem is now ruled out and any MAF DTC code is a false code set by something else. In other words stop looking at your MAF.

Thanks for the replies, unplugging the MAF gave me 2 new codes, 'MAF input high' and 'air temp sensor input high' which I guess are the 2 codes you are referring to. Car seems to drive ok without the MAF, but I haven't driven it far yet.

My new MAF sensor arrived from Germany, I fitted it and... nothing. Well, exactly the same as before:

P0101 - Mass or Volume Air Flow Circuit Range/Performance Problem
P2463 - Diesel Particulate Filter Restriction Soot Accumulation

Live data figures for the MAF whilst driving were pretty much the same as before, so either this new MAF is faulty (unlikely) or my previous one is ok.

 

[HITECH]

When u ran the car with MAF disconnected. Did u clear all codes first ? As in ignition on, engine off - clear all error codes. Ignition off then repeat that a second time. Then ignition off, OBD unplugged, key out of ignition for 5 minutes THEN unplug MAF. Leave for 5 minutes THEN try driving for 1 day.

Aye, I ran but just for a few miles,
with mine both MAF's run the same, plugged or unplugged it runs the same.

What does that tell us?

 

[Problems]

When u ran the car with MAF disconnected. Did u clear all codes first ? As in ignition on, engine off - clear all error codes. Ignition off then repeat that a second time. Then ignition off, OBD unplugged, key out of ignition for 5 minutes THEN unplug MAF. Leave for 5 minutes THEN try driving for 1 day.

I reset the codes, checked that they were cleared and engine light off, then drove with the MAF disconnected. I don’t think I waited for 5 mins, does that make a difference? I got the same soot code back straight away and another 2 codes relating to the MAF “circuit high” and inlet air temp sensor “circuit high” which I think is normal as the MAF has a temp sensor built in. It drove just as it did before, what does that mean?