xc90 dpf and limp mode

[steve777]

Hi

I have been trying to learn about the dpf system now I'm having problems and your forum has been a great source of information but I'd be grateful of some advice to my situation

I have a 2006 xc90 D5 142000 miles. The car would occasionally go into limp mode saying soot filter full if i revved very hard to overtake for example. this first happened about a year ago. The message would disappear once the ignition was switched off for a minute or so. The car doesnt get used daily but most of its use is long distances. The first time the fault occurred was immediately after a weekend trip to kent (600 mile round trip)

The last couple of months it has got worse so that you have to be very very gentle with the accelerator on a hill or it will go straight to limp mode and soot filter full message. Again switching off for a minute will reset it.

My local mechanic did a forced regeneration which didnt make much difference.

He next removed the dpf and soaked it in a chemical over the weekend and washed it out. It was great and i could drive as hard as i could and the problem did not return.

But 400 miles later the limp mode and message returned.

The dpf readings were off 0, idle 24, 2000rpm 70 before dpf was washed out

idle 10-12, 2000rpm 27 after dpf washed out

When I went back after 400 miles idle 47, 2000rpm 105

then did another forced regen which took about 30 mins

idle 20, 2000rpm 34

the soot reading was 3.79g

The fault codes showing are 6665 glow plug relay and 4490 egr position sensor signal too high.

The car will be going back as soon as my van is repaired (fan belt broke, took out cambelt, bent pistons!) so I am using the xc90 for work and driving very carefully which is quite difficult in hilly cornwall!

The mechanic is planning to clean the egr.

Do you think that an egr fault would block the filter this quickly?

The car uses oil at about .5 litre per 1000 miles. It has used a similar amount for the 3 years we have owned it.

After reading a similar problem on a thread from 8th April 2012 I am wondering if the sensor is at fault after all. We had ruled that out as the readings seem sensible.

Is it worth changing the sensor and / or pipes at this stage?

Any ideas or suggestions would be gratefully received


Many thanks

Steve

[steve777]

Can anyone offer me any advice?

[JRL]

I do a twenty to thirty minute drive at 60 in fourth in my D5 once a month as that seems to be the only way to keep the DPF from sooting up. In my case I have only ever seen the soot filter full message once. What I do get though is rising oil level as diesel is mixed with the oil due to the DPF trying to do a regen but failing.

My theory is that the DPF never gets hot enough to complete a regen during normal driving even on a long trip because sixth gear is simply too high. The same thing may be happening to you. If the forced regen worked but you have problems during normal driving then that would suggest regen is failing due to exhaust temps not being high enough.

[colinbos]

Steve,

Ive had similar problems recently. After extensive searching I found that I had an intake air leak that was causing several problems. The leak causes excess soot which in turn fills the DPF and results in bad burn rate.

The first leak was the seals on the Resonator box. I replaced that with a Rubber hose specifically to replace the ever problematic resonator. £50 from Parts for Volvos. I also had a Electronic Throttle Module that was carboned up and giving false readings. That caused my limp mode. The ETM failed big style so after paying Volvo £400 and 20mins to fit I had a fully function car once again.

I would get a full intake check, including the Intercooler and pipes. An intake air leak could cause your problems. HTH.

Good luck

[paulsocksconroy]

I had similar problem with my brothers xc90 it was contanly coming up with soot filt full . So i removed the dpf and sent it to a local company that done a deep clean on it but was still getting the problem after refitting and re setting the ash content ect. I discovered when doing a forced regeneration that the upstream catalyst temp sensor value would jump about and giving crazy readings . So we replaced the sensor andit has been ok since . Hope this helps . This was the ensor up the catalyst not the dpf pressure sensor

[toby1479]

Steve, I had similar issues a few months ago.

Going up steep(ish) hills, overtaking, generally accelerating harder than normal etc, I would get Limp Home Mode and a message saying soot filter full. The worst time was during a weekend away in Swansea, going up a particularly steep hill, with no power due to LHM, not managing more than 5MPH with foot to the floor!!!

Anyway, went to my local dealership (MRG in Chippenham), who without even examining the car diagnosed a potential Intake pipe split the same as Colinbos, this was confirmed with the car on the ramps. They were good enough to not charge me for diagnosis as it literally took 5 mins. The pipe was duly replaced at a cost of around £320 IIRC, inc labour.

As it was explained to me at the time by the Technician, the reason it fails is that the pipe is attached to the sump by a plastic bracket that over time, due to vibration etc, fails. This then means that the plastic pipe is unsupported, and so under it's own weight and again due to vibration, it also cracks and splits.

The reason for the errors is that the MAF (Mass Air Flow) sensor near the intake box detects a certain amount of air, for which the car injects the appropriate amount of fuel, however due to the leak, less air is received at the Intake manifold, causing over-fueling. In a non-DPF car, this would show itself as black smoke from the exhaust, however the DPF removes all of this soot, so there is no visual indication. This black soot is the reason that the DPF becomes blocked so easily.

Since my pipe was changed, I have had no issues at all, no matter how hard I accelerate up steep hills.

[fyall]

are you talking about this pipe possibly being split:

rad_int_054_zps9ed27ca6.jpg

[colinbos]

No, The pipe underneath the car which has the resonator box attached.

[avolvoowner]

Hi Steve,
Can you help please? I currently have the same symptoms as this, did you ever solve the issue?

[ian ferguson]

Hi, my car goes into limp mode on a hill. before this happened we heard a faint whine or whistle, my wife said it sounded like sucking air, any ideas if this could be related. as soon as i can i will look at the pipe under the car, can anyone tell me where it is. Thanks in advance, Ian