D3 4.2TDI DPF issues

[ainarssems]

My D3 is about 175k miles now and as far as I know on original DPFs. A while ago glow lug light came on and there was an error regarding DPF pressure sensor, no effect on performance. I cleared, gave it some beans and it's been fine for about 4 months, error not coming back. I know previous owner replaced a sensor or 2 but there is 4 of them. They are not that expensive but located above gearbox so to access you need to drop subframe with gearbox/engine.

Then couple of days ago I joined dual carriage way full throttle - glow plug light came on again and lost power and max 2.5k rpm. I had to embarrassingly after overtaking everyone pull back in first lane and let everybody by:ROFL: Cycling ignition did not help. This time it came up with DPF efficiency threshold error. Clearing error restored power but going full throttle would bring error and limp mode back. I checked soot values and they were 18-19g calculated and 14-15g measured which is well within limits. I assume because soot is low ECU does not start regen but DPF is partially blocked by ash which does not burn off during regen or maybe oil residue or something, or pressure sensors give wrong readings so at full throttle with a lot of gasses trying to flow through DPFs there is too much pressure differential and it throws fault code.

Anyway did forced regen and then some 20 mile drive in 4th gear, this brought soot level down to 8g calculated, 4g measured, then raised back to 8-9g both calculated and measured. It now works fine and and does not go in limp mode even at full throttle but I think the DPF days are numbered.

So I am thinking DPF removal and remap is in order. Can anyone recommend a place in Midlands, preferably with dyno as well. I see MRC did 2007 Q7 4.2TDI remap about half year ago and got 416PS 957Nm( does not mention anything about DPF) which is quite impressive considering most tuning places only say 375PS. Not sure what it cost but I guess MRC are not cheap.

Depending what the cost difference is I might gut the DPFs myself and just go for remap but would prefer it all to be done by someone else.

[homer simpson]

A lot of places used to do this modification but it has been illegal for a while now so not sure which garages still do this. Even if they do, they are unlikely to advertise it. It is also an MOT failure as the checks are more stringent so not sure if a missing DPF still passes if remapped out.

[ainarssems]

A lot of places used to do this modification but it has been illegal for a while now so not sure which garages still do this. Even if they do, they are unlikely to advertise it. It is also an MOT failure as the checks are more stringent so not sure if a missing DPF still passes if remapped out.

It's not illegal to remove it, you are just not allowed to use it on road with modified emmisions sysetem.:ROFL::ROFL: Regards MOT - yest it's a failure if they know it should be there and they can see it has been removed but normally you leave the can in place just take the guts out either cutting it open on the top where it cannot be seen and welding back up or braking it up in pieces and just pouring out of one end. And you can easily pass smoke test without DPF. My A6 without DPF passes Fast test with about 30% of the smoke limit first try every year. Fast test is the same for all cars DPF or no DPF, if you fail fast test then they look if your car is allowed more smoke.

[Adrian E]

A regen can’t get all the ash out of the DPFs once they’ve aged significantly - it burns off a lot but over time the nooks and crannies fill with ash. Best bet is to take them off and have them chemically cleaned. This removes the ash and restores them to good as new

DPF removal ought, by now, to be considered socially unacceptable, given what we know about the effects of PM10 and PM2.5 on long term health and air quality

Although MOT can be ‘dodged’ still, to a degree, there are still technical moves planned for MOT that will detect smoke opacity levels that exceed whatever is quoted on the VIN plate (number inside a square box, or default values). That may be a factor while the car is still on the road

Given DPFs don’t restrict engine performance to any great degree, chemical cleaning is the cheapest option without leaving a trail of smelly diesel fumes behind you

[ainarssems]

Just a bit of update. Had another occasion of limp mode after heavy throttle and DPF efficiency below threshold error bank 1. Checked soot values and pressure differential straight after and both were within limits. Soot 10-14 out of 68 for full DPF and pressure differential -7..+7 in idle, 7-21 driving, up to 160 full throttle, I understand max limit at full throttle with full DPF is 250mBar. So a bit puzzled why it's throwing up error, could be intermittent fault with one of sensors. So considering a sensor replacement I was looking into doing adaptation for new sensors or to reset DPF ash values if I go down DPF cleaning route.

It turns out that it is not possible with factory firmware and I need to update firmware first. I have stock firmware ending with 10 and I see there are 20 and 40 updates available ( not sure what happened to 30 :) )and there might be newer updates available. Previous owner told me he had some DPF pressure sensors replaced but since the car is still on stock firmware adaption for them could not have been done. I wondering if the sensors have been reading wrong and doing regeneration at wrong times. It's showing 600+km since last regeneration, it has not registered the forced regeneration I did, it was definitely doing it but maybe stopped half way before completing it.

It could even be something entirely different, I understand MAFs, ASV, EGR, exhaust temp sensors, all of them are also tied up with DPF to calculate the volume of gasses flowing through DPF and any of them not working properly could cause DPF errors but they seem to work OK.

I think I will just carry on resetting fault when it appears and let it develop further for now. In the meantime might look at flashing new firmware, I have ODIS, VAS5054 and firmware files but there is always risk when flashing firmware and I do not want to brick ECUs or run into security/immobilizer /component protection problems after update.

[paulrstaylor]

It has been a long time since my DPF issues on a D3, mine was a clear sensor issue and was resolved by replacing both sensors. Back end of the gearbox had to be lowered, not too bad with a ramp but clearly not going to happen on my drive!

The advice at the time was to ditch the DPFs, I wanted to keep them intact.

New sensors plugged in, problem resolved - no firmware issues, no remap needed - no re-occurance and reliable for at least another 60k until I sold the car +++

http://forum.a8parts.co.uk/showthread.php?t=4917

The thinking at the time was fix it sooner than later, as without regen the DPF more likely to end up stuffed up!

[ainarssems]

Well it has been gradually getting worse, happening more often and even at part throttle, seems to happen more when cold. P2002 error was accompanied by P2453 and P2454 this morning, pointing towards sensor. I have checked old paperwork and bank 2 sensor was replaced in 2016 for £252 and it is bank 1 playing up now. I have ordered new sensor, hopefully will arrive by Saturday and I will have a look if I can replace it myself over weekend.

[Johnmed]

Interesting read given I’m at the same mileage (on my 3.0).

Symptoms sound similar, bar the fault codes, to when my turbo suffered carbon build up and went into limp mode.

Keep us posted with your progress.

[paulrstaylor]

On the 3.0 the DPF sensor is easily accessible on the firewall at the rear of the engine.

On the 4.2 they were clearly struggling with packaging, so they fitted them on top of the transmission.

30 mins to replace on the 3.0, officially gearbox out and ~8 hours on the 4.2 :tuttut:

[Johnmed]

On the 3.0 the DPF sensor is easily accessible on the firewall at the rear of the engine.

On the 4.2 they were clearly struggling with packaging, so they fitted them on top of the transmission.

30 mins to replace on the 3.0, oficcially gearbox out and ~8 hours on the 4.2 :tuttut:

Cheers Paul. Ouch:-(

[ainarssems]

On the 3.0 the DPF sensor is easily accessible on the firewall at the rear of the engine.

On the 4.2 they were clearly struggling with packaging, so they fitted them on top of the transmission.

30 mins to replace on the 3.0, oficcially gearbox out and ~8 hours on the 4.2 :tuttut:

I know, right? Could not they find a better place?

According to Elsa it's 0.4 hours for 3.0 TDI, and 1.3 hours for one sensor on 4.2 or 1.6h for both sensors not including adaptation. Gearbox does not have to come out, you just unbolt subframe and lover gearbox a bit to reach to the sensors, still not something I am looking forward to do on drive.

On smaller cars with 2.0TDI it's easily accessible under bonnet, can be done in 5 min.

[paulrstaylor]

It reaistically can be done in much less time, by only lowering the gearbox and having thin arms, but in any case the parts were relatively cheap hence I did both at once.

Sadly for Ainars the previous owner of his decided to save a few quid :Confused:

[paulrstaylor]

I know, right? Could not they find a better place?

According to Elsa it's 0.4 hours for 3.0 TDI, and 1.3 hours for one sensor on 4.2 or 1.6h for both sensors not including adaptation. Gearbox does not have to come out, you just unbolt subframe and lover gearbox a bit to reach to the sensors, still not something I am looking forward to do on drive.

On smaller cars with 2.0TDI it's easily accessible under bonnet, can be done in 5 min.

SOunds like they have changed the procedure in Elsa, but it is absoluetly possible to do it as you say - much easier on a ramp, can see it being a pain on the drive - good luck.

BTW, the 3.0 is the same as the 2.0 - 0.4 hours in Elsa is ~ 5 mins it seems :ROFL:

[ainarssems]

Got the sensors today but the wrong ones. :( at first I thought I have been sent wrong ones but when I checked ebay order they are what I ordered.

I just put in part number 07Z906051A when searching for them and ordered the genuine Audi ones that came up for a good price without double checking the number so have bought 079906051A. I can replicate the results on ebay, searching for 07Z bring up both 07Z and 079. Looking at some aftermarket sensors they are listed as compatible with both 079 and 07Z and also 03G. The difference is 1 mounting hole on 079 and 2 holes on 07Z but since aftermarket parts are listed as compatible with both so electrically they should be the same. I am also not sure they are original Audi, they do have part number on but came without any packaging and were a bit cheap for OEM.

Not sure what to do now, if they were easily accessible under bonnet I would give them a try but considering the work involved I don't really want to mess around. But not doing them tomorrow would mean to wait till next weekend

[homer simpson]

Got the sensors today but the wrong ones. :( at first I thought I have been sent wrong ones but when I checked ebay order they are what I ordered.

I just put in part number 07Z906051A when searching for them and ordered the genuine Audi ones that came up for a good price without double checking the number so have bought 079906051A. I can replicate the results on ebay, searching for 07Z bring up both 07Z and 079. Looking at some aftermarket sensors they are listed as compatible with both 079 and 07Z and also 03G. The difference is 1 mounting hole on 079 and 2 holes on 07Z but since aftermarket parts are listed as compatible with both so electrically they should be the same. I am also not sure they are original Audi, they do have part number on but came without any packaging and were a bit cheap for OEM.

Not sure what to do now, if they were easily accessible under bonnet I would give them a try but considering the work involved I don't really want to mess around. But not doing them tomorrow would mean to wait till next weekend


This is the problem with ebay listings, a lot of sellers put in 'compatible' or similar numbers in their listing specifics to help them gain more exposure. If you are unsure, return them as you don't want to spend all that time and labour for them to be incorrect.

[ainarssems]

I think I will give it a try.

3.0 A6 used 076, 07z and 059 part numbers
3.0 Q7 used 07z and 059, 4.2 Q7 059
A8 3.0 and 4.2 both used 07z

I do not need to fully assemble it to test, I can test and see if it brings up fault code and compare readings to the other bank.

[ainarssems]

The sensor has dies completely now, no readings at all , stays at 0 mBar. No more DPF error P2002, just P2453 for the sensor. This does not throw up error light and no limp mode / reduction in power. So in a way it's good news, I do not need to rush into changing sensor and could send the wrong ones back and get correct.

I understand if the sensor is not working ECU will start regeneration based on the mileage since last regen instead of readings from the sensor. It's not ideal long term but does not stop using car to full potential in the meantime. The problem is sensor could start partially working again and give the wrong readings causing limp mode. I will have a look under car today anyway and see if I still want to try to change it today or maybe unplug it for now if it's possible with less dismantling and wait with change until I get the right ones.

[paulrstaylor]

100% your call, but I ran mine for a couple of weeks, while various dealers tried to work out how to do it, and the symtoms got gradually worse until the "limp mode" was barely able to move the car.

If it does kick in and get to that state, factor in a tow truck! i.e. get breakdown cover if you haven't already +++

Or just use the S4!

[ainarssems]

I had a look last Saturday but opted out of doing it myself :ROFL::ROFL::ROFL: and sent the wrong sensors back for refund. Car has been working without faults most of the week then started getting fault codes again on Friday. As I was not going to change it I was considering remap and DPF removal again, most remap places would not do it. One place that was happy to do it wanted £750, apparently they need to unplug DPF sensors when switching off DPF so it's the same job as changing sensors, dropping subframe with gearbox to get to them.


So I was back looking for a garage to change sensor but most are not interested, must be too busy. It's booked in for Monday now but they refused just to change the sensor and could not give price, said they need to put it on diagnostics and check themselves first for a fixed cost of 0.5 hours labour and then when they have diagnosed it then they can give price for the fix.

[paulrstaylor]

That doesn't sound great, I can understand them wanting to take a look to see what they are getting into, but wanting to charge you to do so isn't great!?

[Adrian E]

That doesn't sound great, I can understand them wanting to take a look to see what they are getting into, but wanting to charge you to do so isn't great!?

Standard practice really - the charge generally taken off the bill assuming you have the work done by that garage. If they only get the cost of doing the scan at least their time is covered. Not many garages are going to want to accept a customer's own diagnosis of a fault without checking it's valid.

[paulrstaylor]

Why not? "Changed xxx at customer request" is a fairly standard disclaimer for doing so?

[Adrian E]

Why not? "Changed xxx at customer request" is a fairly standard disclaimer for doing so?

Because they don't want to get into an argument over a bill for their time if the fault isn't fixed having changed the part the customer thinks is faulty.

There are always options on how to handle, and a lot will depend on the existing relationship with the customer - if it's a 'first time' visit you're less likely to get the customer's opinion of what's wrong taken into account.

It's just a standard 'diagnostic' charge, which is not just for the cost of the equipment, but also the time taken discussing with the customer what they're going to do.

[ainarssems]

It's fixed now and cost only about half of What I was expecting. I got the correct genuine Audi sensor on ebay for £38, I was not sure if garage will use part supplied by me but it was cheap enough to try and and I was looking at possibly saving a day of waiting between them diagnosing the fault and ordering and getting the part.

Monday morning around 9:15 dropped the car off, I was lucky that all 3 fault codes came back before I dropped off car so they could see all of them ( P2002, P2453 and P2454, that's bank 1 DPF below efficiency threshold, Sensor electrical malfunction and sensor implausible signal). Sensor was still in transit at this point. Garage said the car is going in with the next wave and they will give me a call when they find out more. Sensor arrived around 10am. Fast forward to after 2pm still no call from garage, I was going to post office to send a parcel so took the sensor with me and on my way back from post office around 3pm stopped by the garage to see how they are doing.

Apparently they had car hooked up to computer, checked faults and could see sensor and DPF faults, they were thinking DPF is fine, just the sensor faulty but they were not sure so they had sent off data to Audi and awaiting response from Audi and was going to hook up car to computer in 30 min time and see what response they got from Audi and call me as soon as they find out. At this point I say I have original Audi sensor in my pocket if they are happy to use it and save the waiting time ordering part, they were happy to take my part.

Back at home around 3:30pm I get a call from garage and it goes something like this:

Garage - As you know DPF sensor needs changing but it's a lot of work as it is on top of gearbox and we need to remove lot of stuff to get to it
Me - I know, that's why I am not doing it myself and took the car to you
Garage - The problem is there are 2 sensors, computer shows me it's faulty sensor but does not show which one
Me - It's bank 1 , I know
Garage - Which is bank 1?
Me - It's on the right hand side as you sit in the car, cylinders 1-4
Garage - It's a lot of work but we do not know exactly how long it will take or how much it will cost as computer does not show us time required for the job.
Me - Audi standard labour is 1.3 hours. When I first enquired about the job I sent you e-mail, not sure if you have seen it as I never got reply to email and just went to you to speak in person but there was instructions for the job attached as well, I can resend them if you like.
Garage - 1.3 hours? OK, it will be £99.96 all in
Me - Excellent, can you get it done today before closing, If not then I would prefer to take the car today because I need it tomorrow morning and will drop off again tomorrow.
Garage - We will try to get it done today.

About 5pm ( they are closing 5:30pm) I get another call - Unfortunately it's taking longer than expected as everything is seized so we will not get it done today, we will call you tomorrow morning when it's done.

Finally about 11am got a call today that it's done and I can pick up car. I was not sure if they are going to charge me more because it took longer but no, only asked for for £99.96 as quoted, invoice shows 1.55 hours ( I assume 1.3 for the job as per Audi standard labour +0.25 for the diagnostics) @ 59.50 per hour -£8.93 discount(???) +VAT

So all in all happy with the outcome, only cost me £137.96 even if it was a bit long winded process with the garage

[paulrstaylor]

That is a great result.

Does make me smile they have a diagnostic charge, but ultimately you effectivly quoted the job yourself :ROFL:

1.3 hours is the book time, I'm guessing that is on a new car that doesn't have 10+years of corrosion and crud on the subframe bolts that have never been touched!

Let's hope bank 2 sensor lasts longer than the bank 1 did :)

[ainarssems]

Bank 2 was changed in 2016

but ultimately you effectivly quoted the job yourself
that must be why I got £8.93 discount :ROFL:

[paulrstaylor]

Bank 2 was changed in 2016


that must be why I got £8.93 discount :ROFL:

Next time you need work doing, just tell them Audi say it is 1.3 hours +++