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Discussion Starter · #1 ·
Hi. I have just experienced two flashing DPF warning lights within three hundred and fifty miles of each other. The first one followed a period of time when the car appeared to be trying to regen but did not appear to be completing. Fuel consumption dropped and when on the overrun the reading wasn't showing the usual 999.9 miles per gallon. When the DPF light came on the first time I went on a 12 mile journey at 2.5 thousand revs to force the regen but to no avail and I ended up with a flashing warning light. I took the car to the garage and to be fair they forced a regen at no cost to me. However they presumed there was nothing else wrong and I went on my way. I did a couple of long trips and in less than a week same problem but also noticed a couple of days before that the fuel consumption was around 24 to the gallon on a long trip. Took it straight back this time and they checked it on the computer and it transpires that the O2 sensor or Lambda sensor has failed. Causing a drop in power, really poor fuel consumption but more importantly it runs rich filling the DPF and also preventing it from doing a regen. They are fixing it under warranty but part needs to come from Germany.
 

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Interesting; The wife had a (constant) lit DPF symbol come on after she stalledthe carat a junction. The subsequent regen' drive that she did, failed to get it to reset but a couple of ignition on/off sequences had it back to normal.The car has only done 2500 miles and most of that is motorway! I'll be mentioning it to Peter Vardy tomorrow and certainly keeping an eye on it.

Thanks for the info.

-LaZ-

Edited by: Lazarus
 

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Discussion Starter · #4 ·
Just got the car back. What a difference. Makes me think the sensor was playing up for a while. Fair play to the dealer everything done under warranty with no questions. Pleased to have it back . For anyone interested good bit of info about these sensors on this link
http://auto.howstuffworks.com/question257.htm
Seems these sensors only last 30-40k and can get sooted up causing fuel consumption problems.
 

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Discussion Starter · #5 ·
Just had first regen since O2 sensor changed. Took 15 miles to finish but no major problems. About 500 miles done since garage work so was expecting it to happen. Car running very well
 

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Liddy said:
Just had first regen since O2 sensor changed. Took 15 miles to finish but no major problems. About 500 miles done since garage work so was expecting it to happen. Car running very well
That article was about O2 sensors in petrol engines, diesels work differently and have to run lean at low throttle but the general principle is the same.
 

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You should not be doing the manual regen because the car is supposed to do an automatic programme without notification on the dash. The only indication is poor consumption for a while and a nasty niff.

The regen lamp only comes on if the DPF is full and then you have to do the Italian tune-up, the book says over 30mph but better if you can run it up a motorway at over 60mph in 5th (not top gear) for 20 minutes or so (20 miles at 60mph) not just until the regen lamp goes out.
Owner's Manual p.122

If you let it go beyond this stage then the garage/dealership has to force a regen in the workshop to clean out the DPF. They should have done that when they changed the O2 sensor.

If you are having to do a regen drive then you are probably driving too gently and not getting the DPF up to working temperature.

Short 'town' journeys do not help at all: diesels are not suited to journeys of under 10 miles. This can be alleviated by driving more enthusiastically to get the DPF up to cooking temperature more quickly. The occasional thrash up the motorway will also clear the cobwebs out. This does use more fuel but you get less problems with the engine systems. Use the best fuel, it produces less soot.
 

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Discussion Starter · #9 ·
Thanks for that jefrs. The garage did do the manual forced regen twice, first time I took it in and then again within a week when they finally discovered the fault. I do a 34 mile round trip to work and so the engine gets warm enough and I have done 13000 miles myself in the car averaging about 33 mpg overall. I also tow a caravan. When the sensor went it was then averaging 24 to the gallon with obviously the two DPF warning lights. Since the fix the car is averaging 33mpg and is doing regular regens at 500 miles so all is good I hope.
 
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