Y27/9 left EGR positioner signals fault?

[Hussnainh8]

Hello

So I'm stuck now with my ml320 w164 2008, I was very happy I finally sorted the trailer light issue out and was about to start using the car for towing except it runs into limp mode. Towing a trailer isn't going to be a good experience if the car just about pulls it's own weight so can someone tell me why I'm getting this 2511-1 y27/9 positioner fault code? I thought it was a EGR fault so I bought a brand new EGR but replacing it made no difference. Now I don't know what to think or check next......

Thanks.

 

[alexanderfoti]

Have you checked there is power on the connector to it?

 

[Hussnainh8]

Have you checked there is power on the connector to it?

That's something I will check tomorrow morning, Is there anything else to check as well just writing this so I know what to look for tomorrow as a guidance. Worth mentioning my air mass at idle says 481mg with EGR positioner at 5%. If I try actuating the EGR through diagnostic computer it says when active the air mass reading should go down except when I activate, nothing happens. So yes it could be a electrical issue and there could be no power going to EGR. Anything else to check tomorrow?

 

[alexanderfoti]

If you have an active fault code with the egr, it won't actuate, even if the valve is physically OK. It should drop though, yes.

Other conditions need to be correct (engine warmed up etc) even during manual actuation.

 

[Hussnainh8]

Ahhh that explains why nothing happened when I tried actuation. After replacing EGR I assumed I had fixed the fault but then driving home showed it wasn't fixed so when I got home I tried actuation for EGR to see if it will actuate which it didn't because there was a stored fault code (2511-1).. I bet tomorrow if I erase the fault code then try actuating then it will work fine.. which will then get me wondering why it throws EGR fault if EGR is new.

 

[Hussnainh8]

Hello guys

Okay with some more diagnoses I have found it's not the EGR that's faulty as ones I erase the 2511-1 error code and start the car, I can actuate the EGR and the valve opens closes like it should so it gets the power and works like it should.

I then checked live data to see what the values where and boost, EGR and air mass all read values and then change when revved etc BUT the only values I can't see any changes in are the atmospheric pressure and intake air pressure, no matter what I do rev the car to 3k etc those 2 values won't read anything other than 1010 hpa. Maybe I let the revs drop quickly ones and saw it go to 1006hpa but no change other than 1006 or 1010 hpa... This is leading me to believe I need to try a new MAP sensor? Which is my next question, does anyone know where it is located.

 

[alexanderfoti]

Unless you are moving the car to the top of a mountain whilst revving it, the atmospheric pressure won't change.

The intake air pressure will also not change much if the air filter is in good condition.

If you erase the code and go for a mixed drive for 20 minutes, what comes back?

 

[Hussnainh8]

Will go for drive, just saw the state of air filter and decided it's open now so I'm going to replace it. I also saw this connector not connected it's been blocked but not sure what it is for? Goes below the fuel filter

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[alexanderfoti]

Plug is spare, used on some other versions in different chassis. Don't throw parts (MAP) on it before diagnosing.

There should be a boost pressure value that rises when revving, but this won't trigger an egr code!

 

[Hussnainh8]

I can't seem to find any readings for MAP on diagnostic tool, Im using a Autel ms906 so not anything cheap but can't get a reading for MAP. Atleast then I would know if MAP sensor readings are fine.. will just change the air filters and take for a drive as they definitely need replacing! Only just bought the car and was looking to use it for towing and starting my vehicle recovery business but if it stays in limp like this I won't be able to tow anything

 

[Hussnainh8]

Hello

Okay so after replacing the air filters as they were filthy, I didn't get time to drive it yestarday but I took it for a drive today and on cold engine got the engine light straight away (didn't realise I left the MAF and IAT disconnected by accident the night before)

I carried on driving and noticed no drop in performance and was driving perfectly fine the whole way through.

I then reconnected the MAF and IAT and erased the error codes and took for a drive again and noticed the drop in performance pretty much 5 minutes of driving, it went back into limp with MAF and IAT connected up. I then put the diagnostic on it again and saw error code 2511-1 again. Now with the MAF and IAT disconnected earlier when I put diagnostic on it I had codes for MAF and IAT but not this 2511-1 error, it's only showing this after MAF and IAT are connected up so my theory is there is some value in the system which is not right which is throwing the car into limp mode.

But where to go from here as it has a brand new EGR on it now and I can even see the EGR operating properly on cold idle through diagnostic. Worth mentioning I havent been able to get any DPF readings as for some reason there is literally nothing in my ms906 showing anything to do with the DPF. Which I find weird as I know a ML320 definately should have a DPF and I know definately a ms906 diagnostic shouldn't have any problems reading DPF information so why I have 0 information on the DPF is a bit weird. Tried the hot function for DPF regen to see if it will regen but it tells me there are no functions for this. I have seen the exhaust back pressure which is about 1200 hpa which I think is normal so other than that im lost for words.

I can't drive the car with the MAF and IAT disconnected as then I can only imagine how horrid my mpg even though I'm tempted but it's not a real FIX so where do I go from here...

Thank you.

 

[Hussnainh8]

Okay so some more mixed driving with the diagnostic plugged in whilst driving and noticed a few things. First of when the 2511-1 code is logged, the EGR positioner value stays 5% then when erasing the code whilst driving it goes to 95% but will go back to 5% when the 2511-1 code is logged again. With the 2511-1 code it puts it into limp mode but when erasing the code, it goes out of limp mode but goes back in when code is logged. Noticed the code and limp mode occur when giving it the throttle above 2500rpm and air mass values can shoot up to over 1000mg. Also whilst driving the exhaust back pressure can reach 1600 hpa. When 2511-1 code is logged it doesn't throw engine light, this happens few days later if I don't erase the code.

 

[Hussnainh8]

Okay so another drive later and I now have another code with it! So I now have 2511-1 and also 2355-2 which means air mass is too high.

Another thing I have noticed is that whilst driving and monitoring the values, I have noticed the charge pressure is normal but then suddenly it will stay at 27.6% and stay there as if it's stuck and then when I go into the EGR values I see EGR is at 5% and stuck there too. This is all when the limp mode starts.

 

[Hussnainh8]

Anyone? Please I'm desperate in this situation need it fixed so I can start working again as use the car for work. Tempted to just keep the MAF unplugged but how much difference will this make in terms of MPG etc

 

[Supernoodle]

All those tests you've done are just normal behaviour in the event of a fault.

EGR is closed loop control system. EGR valve position is controlled to achieve a specific air flow, as determined by the MAF. If you disconnect the MAF you remove a critical part of that closed loop system. So the EGR cannot be operated correctly. Therefore ECU will prevent that EGR error appearing as it knows there a problem with a input needed for its operation, ie MAF.

Many faults (usually non electrical) will not put a MIL on straight away. They will go pending for several drive cycles (often 3) before they become confirmed and put the light on. That is to ensure there really is a fault.

When the fault occurs out should store some freeze frame data, conditions when the fault actually set. If MB did it properly it would have air flow and EGR demand at the time. That would help you understand what's going on.

The EGR is proportional, it should not just be 5% or 95%, that's just fully closed and open. You need to test it across the whole range. Sounds like you can't do that in icarsoft.

 

[Hussnainh8]

So I guess it's either another new EGR to try or to get the EGR system deleted completely to prevent it going into limp constantly? Tempted to just get the system deleted as have wasted too much time on it.

 

[dougraiyat]

So I guess it's either another new EGR to try or to get the EGR system deleted completely to prevent it going into limp constantly? Tempted to just get the system deleted as have wasted too much time on it.

hi mate did you sort your problem