Strange DPF data reading after battery was disconnected

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S1ngler
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Joined: Sat Mar 11, 2023 2:51 am

Strange DPF data reading after battery was disconnected

Post by S1ngler » Sun May 14, 2023 12:53 am

Hello,
I went to local garage to repair car (nothing to do with DPF or exhaust system) and mechanic disconnected battery while he was repairing the car (2.0 TDI 110 HP 2014). Right after connecting the battery again I've run VAG DPF and it said that distance since last regeneration is 0Km and Soot Mass Calculated about 5g which indicated that DPF regeneration has just finished. But one kilometer before DPF was about just 50% filled. This was strange to me and after about 200km when DPF should be 100% filled I've started manual regeneration from VCDS. And after that I drove about 150km (regeneration usually occurs in 300-350km) and again started VAG DPF and it said DPF is 42% filled (Soot Mass Calculated about 11g). But suddenly after couple minutes and couple kilometers it said again that distance since last regeneration is 0Km, but this time Soot Mass Calculated 8.89g and 37% filled after 0 kilometers driven. Also very strange thing is that fuel tank was below 1/4 full and regeneration shouldn't occur with so small amount of fuel!
What is happening to my DPF, are some sensors bad, or application readings are wrong (compared them to VCDS readings and they are the same)? Can I do something to fix this behavior?
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admin
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Re: Strange DPF data reading after battery was disconnected

Post by admin » Sun May 14, 2023 1:54 pm

After a battery disconnection, it seems there are specific routines for the DPF management, different from the standard.
I think this is an emergency behavior introduced to prevent risk of fire. For the PDF management, the ECU uses also historical data to better pilot the regenerations. In my opinion, when some information is missing, historical data or some sensor value, the ECU acts in emergency mode launching regenerations more frequently considering the worst case for each parameter.
usually after some hundreds ok km, the DPF management should turno to standard routines.
My advise is to wait 3-500km and keep checking the parameters, but considering normal all changes that anticipate the regeneration, they should be part of the emergency mode.
Obviously, these are only my hypothesis based on users feedback, there isn't an user manual for the PDF system.

S1ngler
Posts: 5
Joined: Sat Mar 11, 2023 2:51 am

Re: Strange DPF data reading after battery was disconnected

Post by S1ngler » Thu May 18, 2023 11:08 am

I hope this is just emergency behavior caused by battery disconnection and regular regeneration routine will come back after some kilometers traveled.
But another thing is bothering me - as I said before after I started VAG DPF application DPF was 42% filled (Soot Mass Calculated about 11g) and fuel tank was significantly below 1/4 full and suddenly after couple minutes and couple kilometers it said again that distance since last regeneration is 0Km - so it means regeneration has been done in just couple minutes without car moving which is too short! Also this time after regeneration Soot Mass Calculated is 8.89g and 37% filled after 0 kilometers driven which is also too much it should be about 5g and about 22% filled. It means that regeneration hasn't been done to the end or something is wrong with sensors. How could this happen?

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admin
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Re: Strange DPF data reading after battery was disconnected

Post by admin » Fri May 19, 2023 10:08 am

Sometimes those value become senseless just because they can be altered by the ECU as needed.
For example, in case of sensor failure (usually the differential pressure one) the ecu suddenly raises the calculated soot mass value to the regeneration limit to force the start of the regeneration. Obviously it's impossibile a so sudden big increment, but this is the way the ECU uses to force the regeneration.
I bet that it changes also other values to reduce the risk of fire and make the filter working in a safe condition.
Due to the fact that you're running in a sort of emergency mode, I think that the values you see may have been voluntarily altered by the ECU, but you should keep monitoging them to understand if they're going to revert to a normal range. This should happen in 3-500 km, but this is only a statistic value coming from user feedbacks.

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