S212 2013 Diesel MAF issue - maybe

[alandyman]

Hi,
love my merc BUT it's just started playing up. It's a 2013 bluetec diesel manual s212 (that's the estate right)

I'm getting the engine warning light and using an ODB scanner and app I'm getting MAF(P0101) and DPF partially blocked errors (P2463)
My feeling is that the DPF error may be because it's not doing a burn because of the error from the MAF - not sure.

car revs to 3kRPM then limits and is very low on power

I have tried replacing the MAF with a new one and it produces the same error. (just plug and play right - no initialising/cal of sensor to do on fitting, or am I missing a step here?)

Live data from the ODB shows the MAF airflow rate at idle around 18g/s which I believe should be around 7g/s (same reading with both MAF fitted)
I can think of many reasons the MAF would read low like a split air hose etc but none why it would read high.

Anyone got any ideas, very keen to fix this ASAP

 

[supernoodle]

7g/s could only be with EGR active. I'm guessing with those faults EGR is not active, in which case 14 g/s would be more typical. So yours is still high. See thread below for how to calculate.

What if you MAF reading in g/s?

Hello to you all, I wanted to understand what is the usual reading of a MAF sensor on your car? There seems to be no data on this anywhere. Most people have OBD readers that can tell you what it is with live data. This should help anyone trying to determine if their MAF is bad (like me ). Mine...

forums.mercedesclub.org.uk

There are diag reset routines for MAF and filter replacement for most Mercs to reset the air mass adaption. It's a drift compensation function. If you've had a leak or blocked filter previously it could learn a positive offset. If you then correct the problem without resetting those adaptions, it will give high readings.

 

[alandyman]

thanks for the reply, that sounds like a dealer only job. Maybe that's my route to go. I think from what you said above and the link that the MAF isn't the issue. I guess it's possible that the idle is fine and that I have a leak causing a low reading at high RPM, I'll have a look for split hoses in case it's the range high on the DPF that's off caused by a leak. Any idea what the MAF reading should be at say 2000RPM in neutral?

Could the issue be the other way around and its the DPF blocking that's the source of it all - maybe I should get one of these firms to come round and 'deep clean' the DPF?

 

[supernoodle]

There's no doubt your MAF is high. That calculation I gave in the linked post is the max. It is impossible for it to be higher than 16.33g/s at idle. The calc is there if you want to work out at other engine speeds.

The MAF reset is function is available on even the icarsoft, so should be there on most decent tools. May be on Xentry you can see the adaption values too.

A blocked/restricted DPF occurs as a result of some other issue. Not the other way around.