Frequent DPF Regeneration

[Luey]

I've posted on the forums a couple times in the past about an issue I'm having with me A3 8P 2.0 TDI (170) Quattro. 

I have now established that my DPF is regenerating every 30 miles... which is far too frequent.

My OBDEleven diagnostics tool shows that the filter has 65 grams of ash and a -18% value...

I'm not entirely sure if you are supposed to take the 18% value off the 65 grams to reveal a true ash load of 53%... zero information online

I'm not even convinced these numbers are correct. 

I'm hoping someone knows how to establish whether a DPF is critically full of ash or whether sensors are reading incorrectly and need re-calibrating. 

Additionally, it would be helpful to know if you can reset the differential pressure sensor to recalculate the soot and ash loads? 

Also worth noting that there are zero fault codes on the car and the car always successfully actively regenerates fully.

I've had a quote of £850 for the physical removal, refit and cleaning of the DPF... but I've not taken it for an official diagnosis yet. 

Any ideas would be appreciated. I've done two weeks of research and I'm desperately in need of help. 

 

 

 

 

 

[Southampton Graham]

Hi Luey

I had a similar problem in august last year.

The symptoms were that the fuel consumption was horrendous as in about 30 mpg

The radiator fan was always running when I stopped and continued for about 5 mins afterwards.

I had it checked out and it turned out to be the DPF sensor(Exhaust pressure sensor) at a cost of £50.

 

Hope this info helps

 

[Luey]

2 hours ago, Southampton Graham said:

Hi Luey

I had a similar problem in august last year.

The symptoms were that the fuel consumption was horrendous as in about 30 mpg

The radiator fan was always running when I stopped and continued for about 5 mins afterwards.

I had it checked out and it turned out to be the DPF sensor(Exhaust pressure sensor) at a cost of £50.

 

Hope this info helps

 

I've wondered whether the differential pressure sensor could be faulty. 

Question: Did you have a fault code to say the sensor had failed? Also how often did you find it regenerating?

I've got no faults at the moment.

I also used my diagnostics tool to chart the pressure sensor on a drive. The values don't read anything crazy like negative numbers or sky high numbers. Yet obviously I can't say for sure whether they are in spec and reading correctly. 

I guess this is worth looking into some more. 

[Southampton Graham]

I had no fault codes as i took it to a garage.

It was due a full service anyway and they confirmed it was the sensor during the service.

Checking the invoice it just states DPF Pressure sensor implausible signal but no code.

They checked as I thought is was a coolant fan issue - no stored faults ref cooling fan

it was regenerating every day, especially noticeable when driving into work in the morning.(7 miles to work)

Have you tried a fuel additive to see if that helps clean out the DPF or reduces the number of times it regenerates.

 

[Luey]

Good question. 

I've run the car on Shell Ultimate Diesel for the last 5 months. I also add Redex about every six months as a part of my usual service. I've serviced the car about every 3000 since I've owned it. New EGR valve, swirl flap delete, clean manifold, etc. So everything should be burning cleanly I would expect. 

I also tried K2 DPF cleaner which is a spray in cleaner for the DPF. You add it through the DPF pressure hose. Zero luck with that.

I guess at this point I may need a VAG expert to take a look.

[Southampton Graham]

It sounds like you are using the right diesel and additives.

It must be one of the sensors causing it.

Is your fuel consumption OK?

[The Brummie Mechanic]

Had a few if these with snapped off pipes to the dpf pressure sensor. If you have access to a multimeter, check the 5v source at pin 3 I think, with it unplugged and then see if you have 5v at pin 1 plugged in. If so the sensor is scrap.

[jdragon]

Great info