[turbotel]

Has anyone on the forum succesfully cleared permanently cleared/rectified
the dreaded P0401 code on thier BMW e90.
I have scoured the forums for weeks with numerous posts referring to this code but have found virtually none that have actually fixed this code let alone on a BMW diesel e90.
Please list your success stories in rectifying this code for the benefit of all.

[335dlci]

Originally Posted by turbotel

Has anyone on the forum succesfully cleared permanently cleared/rectified
the dreaded P0401 code on thier BMW e90.
I have scoured the forums for weeks with numerous posts referring to this code but have found virtually none that have actually fixed this code let alone on a BMW diesel e90.
Please list your success stories in rectifying this code for the benefit of all.

What does p0401 mean. P codes are useless.

[turbotel]

Would you care to elaborate and give us less knowledgeable folk the benefit of your experience.
This seems to be one of the most common error codes relating to egr valve function and appears frequently on many forums.
Hardly anyone however reports how they eliminated permanently this code let alone when it refers to a BMW diesel which is my specific question.

[BB_cuda]

335dlci is telling you to get bmw specific codes. He is a experienced tech with lots of BMWs under his belt.

[335dlci]

Originally Posted by BB_cuda

335dlci is telling you to get bmw specific codes. He is a experienced tech with lots of BMWs under his belt.

Yes and also not posting any details about your vehicle doesn't help... like a doctors office ask you age, overall health.. etc. Same applies. Mileage. Lack of upkeep or recent repairs. We aren't crystal ball owners here that can help over the interweb data transmission wiring.

[turbotel]

OK understood,will pull some codes from inpa when vehicle returns .
Thanks for your input

[turbotel]

Ok have narrowed things down somewhat and despite my mechanical knowledge
(was diagnosing and fixing BMWs 50 years ago ! )

Ista has given me code 4501 which refers to EGR problem.

Have vac tested egr valve which opens freely commencing at 14 in/hg (in spec)
and fully opens at 20 ins hg.

Vac is being provided to vacuum rail at 25 in hg.

Solenoid/pressure converter (new but not pierburg) tests ok on bench .

On cold start up with vacuum connected to egr motor stumbles,runs very rough.
This indicates vacuum being supplied by pressure converter.

If motor is started without egr vac connected starts and runs smooth.

If Vac guage is connected at egr connection on startup indicates intermittent pulsing of vac which is obviously causing the bad idle.

In my mind the egr pressure solenoid must be aquiring a signal from the DDE,
but why ?

Surely no signal to open egr pressure solenoid should exist and if so what could be triggering the egr circuit to function at start up and idle.

Once motor has started the egr vac connection can be re connected after a couple of minutes with no detrimental effect.

Is the initial pulses of vac to the egr when engine is cold possibly causing the egr to stick ?

[Nadir Point]

How's the smog regs in the UK these days?

[turbotel]

Emmision regs are due to be tightened in respect of Nox which is increased when dpf is removed.
There is an visual check for excessive smoke and random roadside checks(alledgedly) for emmision system tampering.

Update on my quest to solve my running problems and 4501 code(inpa specific relating to EGR valve )
I will be changing egr solenoid to genuine Pierburg,replacement EGR and replacement exhaust pressure sensor.

I unplugged the original exhaust pressure sensor which restored
air flow readings to nominal readings where previously they were double.

The car performed very well with exhaust pressure sensor unplugged from rubber hose leading to cat and dpf.

Engine idles ok with egr vac connected whereas it was previously very rough.
Feeling as though I am getting close to pinning this problem down but any advice still welcome.

[jacbo]

that's interesting how the engine performed without the exhaust pressure sensor. Do keep us updated as I've has EGR codes ever since I replaced my old EGR valve. The car drives fine without issues but just have the codes popping up every time. I've replaced other parts of the EGR system as well but no luck.

Soon enough I'll be tempted to do an EGR delete as I'm losing patience with this thing.

[turbotel]

I know exactly how you feel,this is testing my patience to the limits.

I even booked iit in to a BMW independent specialist( ????) for diagnostic and estimation .
All they could come up with was a £1500.00 estimate to investigate further with no guarantee of a fix.

Needless to say I pulled the car out of there after having to wait for two weeks for what amounted to a couple of hours work.

I guess in this modern day and age its more lucrative to become a motor mechanic than a doctor.

Even though I am 70 years old and not as flexible as before there are limits and when they take the piss its time for a sharp exit and keep trying to sort it out yourself.
These damn emmision systems .
I will be asking Scotty Kilmer for his advice soon.

[turbotel]

[jacbo]

Originally Posted by turbotel

Attachment 2735464

Is this what you have done or just sharing what someone else has done on a different forum?

I might look into this... my car is on 140k+ miles so wouldn't surprise me if some of the sensors are not quite up to their best performance

[turbotel]

This was my personal fix following my local independent BMW advanced technician being unable to rectify the problem.

[jacbo]

Originally Posted by turbotel

This was my personal fix following my local independent BMW advanced technician being unable to rectify the problem.

Awesome! Good work mate. I have replaced some of the vacuum lines already but will complete that job first, then move onto getting some new sensors in