W221 2011 350 CDI Left exhaust pressure sensor too high

[Aaron75]

My vehicles has 79k mikes I have it serviced regular and do long journeys. At last service I had oil breather and pipe and seals replaced and had the Intercooler pressure checked and cleaned, to give longevity to EGR, Turbo and prevent oil / soot build up in Inlet pipes. I had noticed it go into limp prior to doing this, but it was an isolated incident. No check lights etc.
However recently whilst on long journeys I noticed that I lose boost but I manage to keep the car above 2500 revs to keep momentum up to stop me going at a snails pace from going into limp mode. As soon as it drops to 60/70 mph you’re stuck at no boost, until switch off and on. The car drives fine around town it intermittently goes into limp mode but ive never had CEL check light.


Read codes on a Snap On Solus
Ultra

2359 Charge pressure control. Too low boost pressure
2385 EGR control. Mass Air too large

2696 Check component B60/1 (Left exhaust back pressure sensor) Control variation - The exhaust back pressure too high

DPF Menu Live Data

RPM idle 700
Ash content 6
Soot content of DPF. 77.6
Distance driven single last regen. 181

B60 Exhaust back pressure sensor
HPA 1238

B28/12 Left Pressure Differential sensor DPF HPA 800

B28/13 Right Pressure Differential sensor DPF HPA 15

B28/8 Pressure differential sensor DPF HPA 15

I’m guessing the charge pressure low boost and EGR Mass Air flow deviationis triggered by the faulty high back pressure fault.

It’s clear to see the Left pressure sensor is reading very high, 800
I want to know if it’s faulty sensor and where exactly is it located ? Is it on Left bank manifold ? All threads I’ve read mention one sensor in Turbo and the second near DPF under transmission tunnel.

The DPF soot seems high, the car did complete a regen 181 miles ago when I drove back from London yesterday, Ive read that DPF regen relies upon readings between the sensors being compared but a faulty sensor prevents regen,
I attempted the forced regen after viewing the 70 % plus soot in DPF but it kept failing to perform the regen, error locating signal.

I want a 2nd opinion pls, am I on right track focussing in the left pressure sensor ?
Is this preventing the completion of regen of DPF canusingtge 70% plus soot ?

 

[OneForTheRoad]

Should be next to the egr valve.

 

[Aaron75]

Should be next to the egr valve.

You sure ?
That’s the one that sits near/on Turbo exhaust housing right ? You can see it when you remove top plastic engine cover.
According to the live data above that sensor is denoted as B60 HPA Air Flow is 1238,
Is this a faulty reading, my Understanding it is within normal parameters suggesting this particular sensor is fine. Apparently my car has three sensors. The first one I believe you’re referring to and the other two pressure differential sensor for either cat respectively left and right bank. I’m trying to work out exact location and part numbers. I’ve read other posts and forums relating to 320 CDI’s and they talk about one sensor where you’re referring to and another sensor under the car near the DPF and bolted to chassis.
Mines a later model 350 CDI blue-efficiency and hence it has three. The faulty one is denoted the n live dara above as B28/12 HPA High pressure Airflow is stuck on 800 regardless whether cars off, idling or revving. If DPF was blocked it would go into limp mode and elm light would be on permanently. However the faulty sensor is preventing car self regenning as well as a computer forced regen.
I just want to replace the right sensor and not throw money needlessly.

 

[OneForTheRoad]

Put your vin into 7zap mercedes parts catalogue and search engine electricals.

 

[Aaron75]

Thanks

 

[Aaron75]

Still no joy checked that section and it’s showing the pressure sensor that sits in between EGR and Turbo. I’ve also checked the exhaust system section and it’s only showing the DPF pressure sensor.
I’m confused by the Left and Right Differential pressure sensors depicted by the Diagnostic tool.
Anyone shed light are there two separate pressure sensors that sit on either exhaust manifolds or the respective down pipes going to the catalytic converter / DPF. I’m unsure whether mine has two separate left and right CAT’s ???? Being a late model is this an all in one unit CAT & DPF ????

 

[Aaron75]

Still no joy checked that section and it’s showing the pressure sensor that sits in between EGR and Turbo. I’ve also checked the exhaust system section and it’s only showing the DPF pressure sensor.
I’m confused by the Left and Right Differential pressure sensors depicted by the Diagnostic tool.
Anyone shed light are there two separate pressure sensors that sit on either exhaust manifolds or the respective down pipes going to the catalytic converter / DPF. I’m unsure whether mine has two separate left and right CAT’s ???? Being a late model is this an all in one unit CAT & DPF ????