DPF issue help - P2458

BillyCool

Active Member
Jan 16, 2020
651
248
Leicestershire, UK
The sound is a physical clicking. I wasn't after a fix, even though that would be nice if something is wrong!, it was just to see if yourself or anyone can hear a similar noise during a regen.

I think I've got a video of it somewhere that I was going to show my SEAT service manager, but he wasn't interested...…..

Feel free to share the video. My car is at the garage and won't get it back for a few days so I'll have to check it during the next regen.
 

Skilledmilk

Active Member
Feb 23, 2017
22
3
I've noticed by watching the vag dpf app that my car will regen when it gets to around 120 miles from last regen, regardless of the bar percentage. I've actually seen it jump from around 35% up to 100% and immediately start a regen. I think it's a sensor but there are no fault codes. Anybody else noticed this or prod me in the direction of what sensor it could be?

Just home after a long motorway drive of around 65 miles, in which it started a regen at 110 miles which seems really short. It did jump from 35% to 85 ish when it started the regen.
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BillyCool

Active Member
Jan 16, 2020
651
248
Leicestershire, UK
I've noticed by watching the vag dpf app that my car will regen when it gets to around 120 miles from last regen, regardless of the bar percentage. I've actually seen it jump from around 35% up to 100% and immediately start a regen. I think it's a sensor but there are no fault codes. Anybody else noticed this or prod me in the direction of what sensor it could be?

Just home after a long motorway drive of around 65 miles, in which it started a regen at 110 miles which seems really short. It did jump from 35% to 85 ish when it started the regen.
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Not sure - it does seem a fairly shortish regen gap (c.120 miles) and a bit wierd that it jumps up in value so quickly.

This is purely what I've Googled - There is a DPF sensor that measures pressure and calculates the estimated soot in your DPF based on that and triggers the regen. If this is wonky you may get premature regens if the sensor thinks the soot levels are higher than they are. Can't be sure. It should throw up a fault code but maybe not if it's not actually `broken` but just reading the wrong values (VCDS might pick it up).

It can also be linked to how much soot your car is producing. This can be attributed to incorrect oil, an oil leak or impending turbo implosion (that really screws your DPF). Not sure your car can produce that much is such a short space of time to be the issue and is probably a red herring. I do know that higher mileage cars with a DPF that is getting fuller and fuller with oil as residue (yours is at 60% full) can start to regen more often.

So many variables!

The fact that that figure jumps up so quickly suggests it could be a wonky sensor. From what I've read, they cost c.£25 and can be fitted by you in under 25 mins. Or pay a Stealer c.£200.

Could be something else but I've never seen VAG DPF soot levels leap up like yours does.

Assume your oil levels are good (correct oil?) and everything else seems in order?
 
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Skilledmilk

Active Member
Feb 23, 2017
22
3
I think it's a dodgy sensor somewhere but as you say, there's a few variables that could be having an effect. Aside from the blocked matrix (now fixed) the car is faultless despite the relatively high miles. I've also thought it could be a response to the dog filling up with the oil ash although I can't find any info about that on the old Google. Also, 60% is high but it's also just over half, and if you extrapolate it gives a life of around 230000 miles so I have a while to go!

I'd seen on forums for other diesels that the MAF sensor can potentially cause this behaviour. Might check that also.

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BillyCool

Active Member
Jan 16, 2020
651
248
Leicestershire, UK
I think it's a dodgy sensor somewhere but as you say, there's a few variables that could be having an effect. Aside from the blocked matrix (now fixed) the car is faultless despite the relatively high miles. I've also thought it could be a response to the dog filling up with the oil ash although I can't find any info about that on the old Google. Also, 60% is high but it's also just over half, and if you extrapolate it gives a life of around 230000 miles so I have a while to go!

I'd seen on forums for other diesels that the MAF sensor can potentially cause this behaviour. Might check that also.

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Yeah - like many things, start small/simple/cheap and see how you get on.

MAF sensor can be changed very easily but not sure how that impacts the variable DPF readings from VAG DPF. Good place to start though and then maybe the DPF pressure sensor or whatever it's called.

Nice to know that the car is good for the miles. Mine is a 14 plate (CUPA engine code) with 98,000 and I hope to have it a while.Currently in the garage to have cambelt kit/pump, thermostat (+housing) and new heater matrix. Living the dream!

My previous Mk1 Leon did 220,000 but was pre-DPF and had the lovely PD engine.

Let us know how you get on.
 

Skilledmilk

Active Member
Feb 23, 2017
22
3
Caught the car in the act. First picture is just after I had got to work this morning, commute on motorways for approx 65 miles. The second is just as I was leaving, and it had started a regen. This happens all the time, I've just never been able to catch the exact moment in screenshot.

Can anyone see any issues with the figures on each (aside from the ludicrous jump in soot load). Would a dodgy sensor be the issue here?
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Legojon

I only wanted a remap
Staff member
Moderator
Jul 7, 2015
5,284
2,714
I'm going back a few years to when I had my diesel... but I thought my exhaust temp was measuring nearly 900 degrees at the time of a regeneration.
 

BillyCool

Active Member
Jan 16, 2020
651
248
Leicestershire, UK
Good work on catching that. Based on my experience, your first screenshot looks perfectly `normal` and then on the 2nd one the car thinks you suddenly have a full DPF.

I can only think (based on my limited experience and Google-Fu) that the DPF pressure sensor is faulty. That measures the airflow/pressure through the DPF and calculates the soot load based on that. If the sensor is `detecting` limited airflow, it thinks the DPF is full and needs a regen.

Can't say for sure but from what I've read that's how it works. There are probably other sensors but not sure if they influence the DPF readings.

Would a VCDS check spot that?

Or you have a faulty ECU and many £££'s will be spent.

The bottom line is that something in your car is telling it that a DPF at 37% is suddenly full and that's not right. The good news is, you have a nice clean DPF!

You could try to swap out the sensor (c.£25+your time) but I can't say for sure that's it. I tend to work through the cheaper/easier options and go from there. No idea on your desire to get your hands dirty!
 

SteveGSXR600K1

Active Member
May 6, 2017
579
189
Got to be a sensor issue for it to think the soot mass has gone from 8.27g to 22.7g in 1 mile!

Not sure if it's wanting to start the regen but strange that only one of the post injectors have a value. When mines doing a regen, I have both.
 

Skilledmilk

Active Member
Feb 23, 2017
22
3
Further snooping with the obd adapter and torque app found this in the continuous tests, which I understand are what the car uses to periodically check things are in order.
I have no fault codes and Google isn't much help when looking for the ID's. Does anybody know what the two failed tests relate to? It's odd to me that both have the same value.
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alextz

Active Member
Jun 24, 2020
16
3
Hello @Skilledmilk
Did you manage to get it fixed ? I have the same behaviour. The jump in soot is because your measured soot is higher than calculated and when it reaches the regen limit it copies the value to calculated.
 

plus

Active Member
May 12, 2020
8
4
Spain
I have a question, which OBD do you use for vag dpf? I saw vGate icar but I don't know if is the appropiate, Thanks.
 

BillyCool

Active Member
Jan 16, 2020
651
248
Leicestershire, UK
I have a question, which OBD do you use for vag dpf? I saw vGate icar but I don't know if is the appropiate, Thanks.

 

alextz

Active Member
Jun 24, 2020
16
3
Went out this whole weekend and covered over 1000km. Even on the national roads/highways at around 210-250km regen is triggered by measured soot mass not by calculated.
In the city this is atrocious as a cold start +2-3km of drive gives me around 1-2 grams of soot. I think in the city I can trigger the regen at around 70-80km.

After a regen the soot mass measured goes to -11.85 and calulated to about 4.9-5g.

@Skilledmilk how's yours?

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Skilledmilk

Active Member
Feb 23, 2017
22
3
Went out this whole weekend and covered over 1000km. Even on the national roads/highways at around 210-250km regen is triggered by measured soot mass not by calculated.
In the city this is atrocious as a cold start +2-3km of drive gives me around 1-2 grams of soot. I think in the city I can trigger the regen at around 70-80km.

After a regen the soot mass measured goes to -11.85 and calulated to about 4.9-5g.

@Skilledmilk how's yours?

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My experience is basically the same, I do lots of motorway miles for work and the car basically never does any short trips or stop start town driving. Im still looking at around 80 to 100 miles between regens which given the use case seems very frequent. I have an obd eleven adapter so will check up on the values as you have posted in your screenshot above.

It is puzzling, as I understand that normal behaviour is a regen every 300 or so miles if short trips are not frequent. I'm beginning to think that its maybe a software feature to prevent clogging of the dpf on higher mileage cars and other folks haven't noticed as my car is well above average mileage for its age.
 

Skilledmilk

Active Member
Feb 23, 2017
22
3
I have a question, which OBD do you use for vag dpf? I saw vGate icar but I don't know if is the appropiate, Thanks.
I just used a generic elm327 one from amazon that was about £10. Just checked and the same one is now £32!! I think if all you're doing is reading codes or sensor data for VAGdpf then a cheapo one should be fine.
 

alextz

Active Member
Jun 24, 2020
16
3
Mine is at 100k miles and I do not think that is old. From multiple sources I get the message that the DPF has become clogged. I might try to clean it and see.

Will you get yours at a workshop ?
 

BillyCool

Active Member
Jan 16, 2020
651
248
Leicestershire, UK
Mine is at 100k miles and I do not think that is old. From multiple sources I get the message that the DPF has become clogged. I might try to clean it and see.

Will you get yours at a workshop ?

My 184 TDi has 100,000 miles and seems to regen around every 180 miles. It doesn't do many motorway miles but later this week I will be driving 360 miles, so we'll see how it goes and whether that number increases. I have read that as the car gets older and the DPF fills with the ash residue, it can regen more often. Yours does seem to regen more than it should. What are your VAG DPF figures for your Oil Ash Residue?

It could also be that something else in your car is faulty and the car is sooting up quicker than it should? How often do you change the oil? What oil are you using? I'm using low suplhur 507.00 and change it every 5,000 miles.

If your DPF is clogged then is it completing a regen? Is the DPF light on?

The figures you posted above are what I got from a garage diagnostics as well and made no sense at all. VAG DPF gave much more accurate data to work from. Also check your coolant temp to make sure the car is running ok. Don't use the dash gauges - use your Carista.
 
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