W221 S350CDI BLUETEC LIMP MODE

[Brzu24]

Hello everyone,

I’m new to the forum , i have a w221 S350CDI BLUETEC from 2011 and i have 2 error codes that are bugging me alote.

P0402 Exhaust Gas Recirculation “A” Flow Excessive Detected And
P0101 Mass or Volume Air Flow “A” Circuit Range / Performance

On this stage my car runs in limp mode , basically half of the power , gearbox is changing on high revs and aggressive, fuel consumption it’s higher

I’ve done some live data reading on Idle and i found out that
Exhaust Pressure Sensor Bank 2 it gives me 0 reading on idle or when i rev it (so I’m thinking its a bad sensor )
As well as
Exhaust Gas Temperature Bank 1 Sensor 4 which it’s giving me a reading of -40 c anytime ( so I’m thinking i need to change this one aswell)

( Must say that if i reset the errors , for a short period of time the car pulls like a train and it changes sweet )

My thoughts are that i need to change these 2 sensors and all will be ok

What i don’t know and I could not find on the internet is where is the location for the 2 sensors?

Can anyone please help me with this ? I’ll put some pictures with my findings

Thank you in advance

 

[OneForTheRoad]

Fairly sure , you've only 1 pressure sensor and its right next to the turbo and egr valve . Its meant to read + 0.04 to - 0.04 .

 

[Brzu24]

Fairly sure , you've only 1 pressure sensor and its right next to the turbo and egr valve . Its meant to read + 0.04 to - 0.04 .

Hi bud , thank you for replying , you can see my readings from that sensor next to the turbo and egr valve , but I’ve tested that one so when I unplug it it says 0 instead of 29.90 kPa and gives me an error about that sensor , when i plug it in it’s all good, any idea where its the EgT sensor bank 1 Sensor 4 ? Is it the last one on the exhaust unde the car ?

 

[zipdip]

Well if I was you given where you are I would give CCC a look in they are at29 London Rd Stanway,Chris Cowdrey who runs it with his family is a Bentley man but he's a good guy and they are the ony place I would take a Mercedes where you live..

 

[Brzu24]

Well if I was you given where you are I would give CCC a look in they are at29 London Rd Stanway,Chris Cowdrey who runs it with his family is a Bentley man but he's a good guy and they are the ony place I would take a Mercedes where you live..

Thank you buddy , I’ll give them a call and see

 

[Brzu24]

As a replay guys , I’ve been to cowdray garage and they checked my car and they’ve told me that it is the MAF sensors and they need further checks to see exactly which one are them , I’ve called someone else from Stowmarket Alex, and he told me that I could have a loss of air on the big hose (the one that it’s common fault) . And I should check that first before throwing money on the maf sensors (not cheap at all)

 

[OneForTheRoad]

As a replay guys , I’ve been to cowdray garage and they checked my car and they’ve told me that it is the MAF sensors and they need further checks to see exactly which one are them , I’ve called someone else from Stowmarket Alex, and he told me that I could have a loss of air on the big hose (the one that it’s common fault) . And I should check that first before throwing money on the maf sensors (not cheap at all)

You can try unplugging the mafs to see if faults go . The ecu will take over the readings and fuel the car accordingly.

 

[Brzu24]

You can try unplugging the mafs to see if faults go . The ecu will take over the readings and fuel the car accordingly.

Hi Bud,

I’ve done that (unplug the sensors) and the car doesn’t go in limp mode anymore, drives much better , but it still has some lag on full throttle.

I’m thinking of the common fault of the intercooler hoses for the lag part.

I’ll check the EGR valve to see if it moves when it needs too.

 

[BlackC55]

Do a smoke test first. Then you will see any boost leaks. Its very likely that your air mass sensors are faulty and maybe the EGR valve too.

 

[Brzu24]

Do a smoke test first. Then you will see any boost leaks. Its very likely that your air mass sensors are faulty and maybe the EGR valve too.

I’ve ordered the red seals from turbo and the breather and the turbo inlet ring seal aswell. I’ll change them first as i have a turbo leak on that ring seal.

 

[Brzu24]

Hi all,

After changing the seals and the egr back pressure sensor (oem part) , i only have this error P0402 Exhaust Gas Recirculation “A” Flow Excessive Detected which make my car be like a Tesco trolley, limp mode with less power and around 3000 rpms .

How can i test the egr valve and see if its working properly,

I’ve opened the black plastic cap from the EGR VALVE and it looks new and with new grease, the middle bit moves by hand freely ( the egr valve has been changed by previous keeper as it’s not original and it looks new) could be a cheap aftermarket with a faulty motor for the flap movement?

 

[Larkone]

Get the live data readings for the EGR to see if it is opening and closing - or take it to Alex Crow and let them sort it - highly recommended (it is where I take mine and they are next to the railway station which is useful)

 

[Supernoodle]

Brzu24, I'm guessing you're using the Delphi tool in OBD mode looking at that screen shot. The diag tool requests data from the ECU using PIDs. These are standadised and defined by an ISO. PID 73 is for the exhaust pressure and holds data for two sensors. If the engine only has one, the ECU still has to transmit data for two sensors. That's why bank 1 looks good and bank 2 is 0.
Same story for exhaust temps on PID78, it supports 4 exhaust temps. The - 40 for sensor 4 suggests it's not present on your engine.
In theory those PIDs should also contain information to tell the diag tool which of those sensors are fitted, but I'm not sure if Mercs and the Delphi tool have this implemented properly.

So be careful how you interpret the live data.

 

[Brzu24]

Hello everyone,

Tomorrow I’ll go outside and take the black plastic cap of the EGR valve to se ic it work to open and close as it should, and keep you posted, if not I’ll take it to Alex , cause it do my had in by now

 

[Larkone]

Hello everyone,

Tomorrow I’ll go outside and take the black plastic cap of the EGR valve to se ic it work to open and close as it should, and keep you posted, if not I’ll take it to Alex , cause it do my had in by now

Even if it is moving doesn't mean it is working properly - you need the live data to see if it is moving to the correct required position

 

[Supernoodle]

EGR flow is inferred from the MAF. Throttle is fully open so each intake stroke must fill the cylinder with air (or at least swept volume*volumetric efficiency). When EGR is closed, this should be the MAF value. When EGR is operational the induced volume is unchanged, so if MAF reduces it is assumed to be EGR making up the difference.
Unmetered air entering, ie an intake leak as mentioned earlier, would cause the MAF values to be low too.
A bad MAF and a high exhaust back pressure could do too.

I expect a demand/actual EGR valve position difference to cause a position or governor deviation error rather than the flow error.

 

[Brzu24]

Hy guys

Just a quick update , I’ve took the plastic cap from the EGR VALVE and i saw that the egr valve it was moving a bit when pressing the gas pedal and after a bit it didn’t Move at all , I’ve ordered a new EGR VALVE WAHLER from the internet, I’ll let you all know how it will perform after it arrives.

Thank you all for all your information and interest.

Ps Happy New Year to all !!!

 

[OneForTheRoad]

Fairly sure , you've only 1 pressure sensor and its right next to the turbo and egr valve . Its meant to read + 0.04 to - 0.04 .

^^^^. These are dpf pressure sensor readings and not exhaust readings , the back pressure is something like 980 mb around 16 psi . Anyone reading this thread.

 

[Brzu24]

Hy all,
Managed to take my car to a specialist to find out the code p 156000 with the exhaust gas deviation on high , they’ve done all the checks and couldn’t tell me exactly what it was , so I’m back to square 1.
I wander if it could not be from the thermostat as it take longer to warm up , and inside the heating inside it’s not great as it was other time , takes more time to warm.

I also have fluctuation of outside temperature either 4 degrees (as it should be) either 16.5 ( today) and back to 4 .

Do i have a sensor who it’s not in his place and move’s towards the radiators ?

I’ll check that in the following days and let you know .

The problem with tge p156000 appears when the car get’s warmer towards the ideal temperature.

 

[BlackC55]

I expect the intake is blocked or an EGR pipe is too.