V70: Engine Soot Filter message not as advertised

[crewman]

I spoke with my friendly neighbourhood mechanic this afternoon - he'd awarded himself a two week christmas break - his immediate comment when I described the symptoms was faulty sensor. The car is booked in with him for next monday, if he's right a replacement sensor should be a lot less than a new DPF. Thanks to all for your input.

[Clan]

Originally Posted by crewman

The engine is D5244T, the mileage is an unknown. The odometer says 108000 but since I bought it I have discovered that the MOT history suggests a speedo change when the car was 3 or 4 years old. Best estimate is somewhere in the low to mid 200s.

when you have a new speedo the current mileage is automatically taken from another module in the car where it is also stored and loaded into the new one .

[tommyweaves]

Originally Posted by Tatsfield

If there was insufficient heat, wouldn't the result be that the filter was not regenerating and if so the pressure sensor would be registering a high pressure caused by the unremoved obstruction? The diagnostic is saying that the pressure readout from the sensor is too low not too high. Since it is not possible for the genuine pressure to be too low for any mechanical reason, the only alternative would be that the readout is false and that is probably a faulty sensor.

If I was the OP I'd be praying that your excellent logic is correct and it's a faulty sensor!

Needless to say that the regen process CREATES additional heat by overfuelling, therefore making the Italian tune-up unnecessary. This however I believe creates too much regular additional heat in the cylinder head leading to oil break down (particularly if you use inferior/wrong spec oil) in valve lifters which then fail - then you start burning oil, and that gooses your dpf.

[green van man]

So are you saying change the oil after a forced regen or normal regen damages the oil?

I can see a case for both but would expect correctly specified oil changed at or before set intervals which are 1 year OR 18,000 miles to be able to survive the regens that occurs aprox every 500 miles if my reading of the handbook is correct. My understanding is that 8% of diesel is injected on the exhaust stroke to burn in the dpf normally to keep it clean and this figure raises to 30% during regen cycle.
I may of course be wrong and stand to be corrected, niether do I like the idea of sump oil being diluted with diesel but as my car regularly does a 200 mile round trip 100 of which are motorway or duel carriageway and only does 10,000 a year I am hopeful that no lasting damage is being done to the specified oil and therefore the engine.

Paul.

[tommyweaves]

Originally Posted by green van man

So are you saying change the oil after a forced regen or normal regen damages the oil?

I can see a case for both but would expect correctly specified oil changed at or before set intervals which are 1 year OR 18,000 miles to be able to survive the regens that occurs aprox every 500 miles if my reading of the handbook is correct. My understanding is that 8% of diesel is injected on the exhaust stroke to burn in the dpf normally to keep it clean and this figure raises to 30% during regen cycle.
I may of course be wrong and stand to be corrected, niether do I like the idea of sump oil being diluted with diesel but as my car regularly does a 200 mile round trip 100 of which are motorway or duel carriageway and only does 10,000 a year I am hopeful that no lasting damage is being done to the specified oil and therefore the engine.

Paul.

Paul, It's just a hypothesis I have for why a number of higher mileage D5s suffer from this soot filter full/limp mode/dpf problem. I would expect, as you say, correct oil at the correct intervals will prevent failures; but I suspect there are plenty of high milers that have NOT had either the correct oil or at the correct intervals which could lead to problems. In addition to this the problem is exacerbated by the diesel dilution of the oil which was a known issue. There are plenty of Gen 2 threads on the whole issue and it wouldn't surprise me if the same problems are now affecting older Gen 3 cars.

I suspect the dealers don't see much of these higher mileage cars and therefore there is very little definitive information on why/how these issues occur.

It's entirely possible of course that I'm talking out of my hat, but if my 163 D3 starts making a whoomping noise near the airbox or I get the soot filter full message more than once I'll be selling promptly, even though it has a full Volvo service history from new in 2010 and has only done 103k.

I hope the OP comes back and posts whether or not a new sensor fixes the problem!