Volvo XC90 - D5244T4

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Volvo XC90 - D5244T4

Postby STC » Wed Nov 16, 2016 2:15 am

This has 2 re occurring fault codes
1. Glow Plug - Permanent Fault, Returns each time Ignition is cycled
2. DPF Pressure Sensor - Faulty Signal - Causing Limp Home Strategy and MIL Illuminated.

I have looked into the glow plugs with an Amp Clamp and one of them is not drawing any current. I have not replaced it yet as I don't think it has any concern with the DPF Pressure Sensor Fault. Perhaps that is my mistake ?

I did have some graphed Actual Values but seem to have lost them, will collect some data again and post.

I have started so might as well put down what I do have for now.

It already has had a new Genuine Pressure Sensor, adaptation has been carried out. I have made sure the Pipes are Clean, Clear and not leaking, Used a Mityvac to verify the Sensor is accurate in line with Actual Values. Sensor Wiring, 5v Ref & Ground is not an issue, all tested fine.

With the fault Cleared the car has plenty of power and will be fine until my foot is taken off the pedal and the Pressure sensor value will drop to near Zero, if it remains near zero for 4-5 seconds the DTC will set.

I have driven this car for the last 3000 miles, It has not gotten any worse or better

Under hard load the Pressure sensor will only get up as far as 400 mBar (relative), and as mentioned does not set the DTC. Or is it waiting for me to slow down to put into limp home when safe to do so ??

It also has a vibration through the car and steering wheel only at idle.

In an Ideal world I am looking for a known good waveform for the pressure sensor, DTC setting criteria and whatever else you think maybe appropriate.

I will post again with Scope trace of Pressure Sensor and something to give an indication of engine speed, Live data Graphs etc.

As always, any assistance gratefully received.

thank you.
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Re: Volvo XC90 - D5244T4

Postby steevegt » Wed Nov 16, 2016 2:46 am

Hi STC

I guess that with the glow plug problem, the engine computer may not do active DPF regeneration. This at least will increase the saturation of the DFP in long term.
Maybe that DTC is set based on a calculated DPF saturation that will not drop below 100% because of the above problem. It just waits a little to be in memory after it is erased!?

It can be just because 400 mbar is too much pressure, but the timing of the DTC is not in sync with the pressure peak!?

If it was me, I would fix the glow plug problem first, do some miles with the car waiting for it to do the active regeneration that it may need, and that may just fix 2 problems. Makes sense?
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Re: Volvo XC90 - D5244T4

Postby volrem » Wed Nov 16, 2016 12:30 pm

What are real DTC codes?

Faulty glow plug does not cause DPF pressure sensor faults and regeneration is still active.

400 mbar pressure is too much.

I have uploaded some captures for DPF pressure sensor into waveform library. Maybe not XC90 but other older models use the same sensor with some exeptions.
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Re: Volvo XC90 - D5244T4

Postby steevegt » Wed Nov 16, 2016 2:31 pm

volrem wrote:Faulty glow plug does not cause DPF pressure sensor faults...


For sure. At least not directly I guess...

volrem wrote:...regeneration is still active.


Are you 100% on this? Do you have evidence or documentation to back it up?

There are some faults that disable the active regeneration process. I have witness that in a permanent EGR circuit fault for instance.
This looks like it has a permanent glow plug fault for a long time. If this system does not do active regeneration because of this, the high pressure and the DTC for the pressure sensor, could just be caused by a clogged DPF.

Not saying that this is the case in this XC90, but it looks plausible to me.
Anyway, even if you think that is very remote, addressing the glow plug first may be the wisest thing to do, as it needs to be done anyway, and in the end it may just be the cause...
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Re: Volvo XC90 - D5244T4

Postby volrem » Wed Nov 16, 2016 4:10 pm

steevegt wrote:
volrem wrote:...regeneration is still active.


Are you 100% on this? Do you have evidence or documentation to back it up?

There are some faults that disable the active regeneration process. I have witness that in a permanent EGR circuit fault for instance.


Yes I'm 100% on this. I have seen many cars that have glow plug fault code stored and they still regenerate without issue.
I work with these Volvo diesels every day and newer had issue with that.

I don't thik one faulty plug will have any effect but when all five are dead then probably it wil affect regeneration. But not disable it completely. EGR is different thing and affects for sure.

I don't have any documentation that backs this up. But I have documentation for that glow plug code that states there is no substitute value (dpf regen stopped for example) and may only cause poor starting.

I agree that this faulty plug(s) need to be replaced but I'm sure there are other causes for that DPF problem.
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Re: Volvo XC90 - D5244T4

Postby steevegt » Wed Nov 16, 2016 5:02 pm

volrem wrote:Yes I'm 100% on this. I have seen many cars that have glow plug fault code stored and they still regenerate without issue.
I work with these Volvo diesels every day and newer had issue with that.
...


Permanent codes or temporary codes? If permanent for how long they have the code? How did you validate that they will do and active regeneration with a permanent glow plug code?
Even if you did validate all the above, the software version may be different in here, we never know...

volrem wrote:...
I don't thik one faulty plug will have any effect but when all five are dead then probably it wil affect regeneration. But not disable it completely. EGR is different thing and affects for sure.
...


Maybe a single faulty glow plug does not matters for the DPF to be properly regenerated, I guess, but that does not mean that the software will not stop from doing it.

volrem wrote:...
I don't have any documentation that backs this up. But I have documentation for that glow plug code that states there is no substitute value (dpf regen stopped for example) and may only cause poor starting.
...


That has some value for sure, but it will not be the first time, or last, that a manufacturer documentation is omissive in something...

volrem wrote:...
I agree that this faulty plug(s) need to be replaced but I'm sure there are other causes for that DPF problem.


For sure you may be right, but I'm not 100% convinced.

I trust your word and knowledge, don't get me wrong on this, but to be 100% is something that is not easy without a scientific validation.
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Re: Volvo XC90 - D5244T4

Postby volrem » Wed Nov 16, 2016 5:34 pm

steevegt wrote:
volrem wrote:Yes I'm 100% on this. I have seen many cars that have glow plug fault code stored and they still regenerate without issue.
I work with these Volvo diesels every day and newer had issue with that.
...


Permanent codes or temporary codes? If permanent for how long they have the code? How did you validate that they will do and active regeneration with a permanent glow plug code?
Even if you did validate all the above, the software version may be different in here, we never know...



Permanent. Anything between few hundred and 20 000+ km. If ECM would stop regeneration then DPF would be clogged very soon. Definately in 20 000 km. I have validated by checking DPF pressure and accumulated soot quantity. Also by driving the car and checking exhaust temperature.

Software version may be different but I seriously doubt that this logic would be different. And there is no MIL for glow plug code.

And still need real DTC-s to check and give suggestions. There are many different DTC-s for glow plug and for DPF.
As far as I remember limp mode is triggered when DPF pressure exceeds 500 mbar.


Glow plug DTC could be glow plug problem and it could be glow plug "relay". Pretty easy to measure though.
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Re: Volvo XC90 - D5244T4

Postby STC » Wed Nov 16, 2016 5:45 pm

Thanks Guys

I too am not 100% convinced that a single Glow Plug issue is going to give me a DPF pressure Sensor - Faulty Signal fault.

However I do agree with you both, it would be foolish not to fix and eliminate that first. It is an easy and cheap repair (I have a feeling that it is a GP Control Unit Fault - Glow Plugs look new)

In the mean time I will take it for a long drive and collect some accurate data and fault codes then post them on here, that may take me a few days.

The car is in my possession for the next few months so no big hurry.


Something to think about
As far as I remember limp mode is triggered when DPF pressure exceeds 500 mbar.


My thoughts are that this car is triggering the DTC when the pressure drops to near Zero and stays there for 4-5 seconds, As I am slowing down if I put into neutral and holds the RPM up above 11 - 1200 rpm until the vehicle speed drops to zero then the DTC will never set.

I'm thinking this is a case of the Differential pressure being too low - not too high. It is difficult to get it up to 400mbar, driving it hard and uphill. Even when it does hit 400mbar it is only for a moment.

I am wondering if someone has removed the internals of the DPF ?
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Re: Volvo XC90 - D5244T4

Postby Dcunning35 » Wed Nov 16, 2016 8:50 pm

I may have tea tho wrong as I'm using phone apologies if I have , the dtc is it p2002 ,can you verify the exhaust pressure physically I just remember having a cmax just as they went from a differential pressure measurement to a single port pressure sensor that logged p2002 everytime on the overun and turned out to be a egr issue . I was just thinking of the circuit is good and adaption reset it only leaves a physical pressure deviation.
Although I may well be wrong .
Hope everything is well with you anyway stc
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Re: Volvo XC90 - D5244T4

Postby STC » Wed Nov 16, 2016 9:46 pm

Hi Danny.

Thanks for the contribution, this does use a differential pressure sensor with 2 pipes and quite likely the same as on the CMAX. It has FoMoCo moulded into it so it is a FORD part and something you will be familiar with.

My next logical step has to be to gather some serial data and fault codes & DTC's from the car before and after the DTC sets and it goes into limp home.

P2002 as far as I recall is not a DTC I have seen on that car.
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