DPF Differential Sensor 'Implausible'.

[M80]

Limp mode, engine light on.
iCarsoft reports the DPF DP has an implausible reading.

There is 5 volts between terminals 2 & 3 at the sensor, and terminal 1 has continuity to the ECU.

I've ordered a new Bosch sensor but wonder if there is possibility that an over full DPF could cause an implausible reading. Hopefully not and the sensor has gone us.

Does implausible always mean the sensor is faulty?

 

[mioba]

I had a google out of interest

Making sense of your sensors: DPF differential pressure sensor

To understand how the DPF differential pressure sensor works, why it fails, and how to replace it when it does, let’s briefly discuss the DPF.

www.delphiautoparts.com

 

[Cole@MBS]

We do up to 5-6 sensors a week, there failing at a alarming rate! You need to flash the engine ecu as well as there is new parameters to match the new sensor!!

 

[alexanderfoti]

Yes, very common! Implausible usually means its offset, EG reading 2 bar at idle with no flow at all. Or 1 bar at 100% load.... Not usually caused by blocked DPF, but if driven long enough with the fault, it will need a clear and regen.

 

[M80]

mioba, thanks.
Most of that I knew, the extra about the testing could be useful, but really the opinions that it would seem that implausible means shot.

Cole I've ordered one with the exact same id number, in hope that updating would be avoided.
The removed sensor is dated Jan 2018, the Viano is 2014, so it isn't original. In that period the vehicle was serviced / looked after by Stevensons (MB Indie near Maidstone I assume), so I would assume it's ok with my new sensor when it arrives.

My concern is that the engine has been overhauled some by me. The injectors have been reconditioned, but not yet coded to the ECU. The reconditioner is able to do that when I'm able to travel to him.
Reluctant to start I hoped that was due to some trapped air, but it puffs black smoke when I accelerate, so some unburn fuel.
Till today it has only been run on the drive for maybe 15 / 20 minutes.

Less than 4 miles into todays road test and this. As it was ok previous I'm unlucky , although these sensors do sound to be unreliable.

 

[alexanderfoti]

mioba, thanks.
Most of that I knew, the extra about the testing could be useful, but really the opinions that it would seem that implausible means shot.

Cole I've ordered one with the exact same id number, in hope that updating would be avoided.
The removed sensor is dated Jan 2018, the Viano is 2014, so it isn't original. In that period the vehicle was serviced / looked after by Stevensons (MB Indie near Maidstone I assume), so I would assume it's ok with my new sensor when it arrives.

My concern is that the engine has been overhauled some by me. The injectors have been reconditioned, but not yet coded to the ECU. The reconditioner is able to do that when I'm able to travel to him.
Reluctant to start I hoped that was due to some trapped air, but it puffs black smoke when I accelerate, so some unburn fuel.
Till today it has only been run on the drive for maybe 15 / 20 minutes.

Less than 4 miles into todays road test and this. As it was ok previous I'm unlucky , although these sensors do sound to be unreliable.

DPF Is shot if you see black smoke in the mirror........

 

[M80]

DPF Is shot if you see black smoke in the mirror........

You mean needs new or needs forced regen?
It isn't smoke in the mirror it's when I push the peddle while sat on the drive, or even as I pull away from standstill. Nothing apparent as I drive.

 

[alexanderfoti]

You mean needs new or needs forced regen?
It isn't smoke in the mirror it's when I push the peddle while sat on the drive, or even as I pull away from standstill. Nothing apparent as I drive.

If you see any visible smoke on the DPF it means there is a pathway through it and that it is not filtering. Not sure how long you have had it, but somebody may have bashed a hole through it etc.

You will get implausible dpf error if the dpf shows no restriction change through the engine load.

 

[M80]

This is feeling like deja vu from my earlier 642 Viano, a total disaster.

Bought Sept 2020,
drove well and happy with all for 3,800 miles, mostly long journeys.

December it failed the MOT on emissions, at 0.39 whatevers.
The only smoke, blackish, was evident if stood still and revved fairly hard. Not a lot but evident on a still day.

Later I saw white smoke for a few seconds on a cold start. With a sweet smell, so seemed to me to be coolant.

Evident from the rising exhaust temperatures it would regen at a little over 400 miles each time.

Seeing that working on anything in the confined engine bay, on an unfamiliar engine, was a bitch I back shelved it till I could find time. then bought the 211.

So 6 months later engine out, injectors tested (well 2 of 'em) they failed so had the 4 reconditioned.

Now it is a reluctant start, can run less than sweet, but also might do, and this fairly low rev puff of smoke.

I suspected air in the fuel system from the injectors having been worked on.

 

[M80]

As you suspected the DP sensor made no difference, so the one that came out is back in. The new sensor can be kept as the spare.

No longer showing as implausible but the EML is up, also down on power some.
Still with the black puff if revved a little.

New DPF is on order, hopefully that'l be here and fitted tomorrow.

My concern here is the puff of black smoke, is that likely to block the new DPF in a short time?
Is it possible that the reconditioned injectors are at fault and causing the puff of black smoke?

 

[mioba]

Whst the EML code showing, same again?

 

[M80]

The code showing is the same as
2454 Particular Filter Pressure Sensor A Circuit Low

 

[M80]

I've just gone under to remove the existing DPF, although still waiting for the new.

I find the rear pressure sensor connector is loose.
Not remembering removing it I'm feeling like senility is setting in, but as I try to reconnect the nut falls apart.

So it seems I've found why the DP sensor isn't happy. And see that anew pressure line is needed.

Even if the car was in regen, as the exhaust temperature was high, I don't see that would explain the reluctant start,
sometimes lumpy tick over,
or the puff of smoke.

Any thoughts?

Edit:
Anyone know where I can source a new union nut?
To me it looks to be a G1/4 with a 9mm pipe hole.

 

[mioba]

Probably because the DPF is full and the gas cant escape.
Glad it seems you have found the problem, get the new DPF sent back.

 

[curious]

Is this what you need ...

https://tameson.com/fittings/hose-pipe-connector/hose-barb/spare-part/f29kh-9mm-g1-4inch-nickel-plated-brass-union-nut-l15p5mm.html

 

[M80]

Is this what you need ...

https://tameson.com/fittings/hose-pipe-connector/hose-barb/spare-part/f29kh-9mm-g1-4inch-nickel-plated-brass-union-nut-l15p5mm.html

Yes that's it,
not sure about it being brass though. But for a few more quids they do the same in stainless.

 

[M80]

Probably because the DPF is full and the gas cant escape.
Glad it seems you have found the problem, get the new DPF sent back.

I took it for a spin with the pressure line held to the exhaust outlet be stainless tie wraps. No codes, more power but no kickdown.

I'm assuming that the DPF is breathing ok, but as Alex, the smoke would indicate that the DPF is faulty. I'll try dropping the exhaust joint off pre Cat, that would eliminate a DPF blockage being the starting issue.

But is some smoke to be expected and the DPF should stop it, or is the smoke indicative of another issue?

 

[mioba]

I would be inclined to get a force regen done and take it from there

 

[mattkh]

I took it for a spin with the pressure line held to the exhaust outlet be stainless tie wraps. No codes, more power but no kickdown.

Was the starting still lumpy,,?

 

[ajlsl600]

W

We do up to 5-6 sensors a week, there failing at a alarming rate! You need to flash the engine ecu as well as there is new parameters to match the new sensor!!

Why am I not surprised on both counts, shite quality ,expensive sensor plus a min charge resetting. Non of that crap on a minx!!