DPF Light and pulled a NOx Fault - Need Advice ASAP

[jesus_man]

You are correct. I too did the same thing with fuel conservation, but found that idling killed my mpgs. I do like to allow the fluids to circulate for a min or so before I start driving, especially in below freezing temps. I also installed the Frost Heater with all the goodies to aid in cold starts and make the commute warmer, quicker.

But, as I mentioned before, once the engine up to operating temp, drop it into sport mode and drive a little more aggressively. If they replace parts on your car, you might just make it a practice to drive that way once a week or for 20-30 min a week and if you have a good highway spell, drop it into manual mode and pull it down a gear to maintain higher rpms. If they do NOT replace anything, then I'd start driving it in sport mode for the first week or two. My guess is you won't see a significant hit to your MPG's, but it will be better for your car, especially when it's on you to repair it!

 

[dbbyleo]

Yes... since learning all this... what you said was exactly what I think I need to do. But I'm concerned that may not be enough. I've only got 3000 miles left on the warranty and there's just a mix of opinions out there as to whether or not these emission issues wont just keep coming back to hunt me.

I wish there was a good way to monitor the system... to know when things have started to build up and then to drive it hard to "burn it off". I've got the VCDS, but haven't gotten any intel from all my research how people are using to gauge soot levels and to know when to do a burn off.

One thing I did learn was the difference between passive and active regen. If I understood this correctly, passive regen occurs just by your normal driving... ie your driving habits is enough to reach high enough temps for regen to occur naturally/passively. Active regen is when the car injects fuel post-combustion to heat up the DPF/NOx so it can regen.

What I don't know is if active regen just occurs in set intervals... or if occurs only when the car detects build up (ie passive regen is not enough). It would be good to know if it's based on car detecting... because I think you can tell when active regen is happening when your idle RPM is slightly elevated than normal.

If I can't use the VCDS to tell when I should do a "burn off", I could rely on when I detect the car us doing an active regen.

Thoughts?

 

[jesus_man]

You are correct in that when the active regen is happening, the car will idle around 1k rpms. That is when I would drop to sport mode and drive a little harder. But when I was having my trouble, often times that seemed too late. I recall several times driving for 45+ minutes trying to get it to complete the process without any success. Even had a 3hr road trip once and it still didn't work! Seemed I could clear the codes with VCDS and then drive it hard for the next few commutes and that would get me some time without the CEL. Even went into limp mode a time or two. But the dpf light would always come back. Perhaps you need to drive in sport mode all winter and occasionally in the summer?? I do think you need to stay ahead of it, which is why I suggest that "every Friday is Sport mode Day" or some such??

I can't say for certain, but I do believe the Active Regen occurs based on a soot level, not based on miles.

 

[dbbyleo]

I will check in at the Ross-Tech forum to see if anyone has any good idea for how to check "soot levels"... because even if I resort to the "Friday sport mode" thing... I'd still like to know if that's enough to stay ahead of things.

 

[jesus_man]

Would love to hear any results. I too have posed the question with no answers.

 

[ShelbyRazorback]

Go here?
https://forums.ross-tech.com/index.php?threads/1220/#post-10610

 

[AverageAndy]

What I don't know is if active regen just occurs in set intervals... or if occurs only when the car detects build up (ie passive regen is not enough). It would be good to know if it's based on car detecting... because I think you can tell when active regen is happening when your idle RPM is slightly elevated than normal.

Yes, during active regen idle RPM will be slightly higher. Also, exhaust gas temps on bank 1 will be a lot higher than normal, such as 200C+ more than normal (mine has gotten up to 600C once). You can monitor this in VCDS. When car is on, VCDS plugged in, go to group 01 engine, then advanced measuring. You will see a pop up when you can select a number of variables. I usually check soot mass, ash load, coolant temp, engine oil temp and exhaust temp bank 1 and 2. My car enters active regen when soot mass is around 20-22gm. You will know it is happening by the sudden rise in exhaust temp, dropping in soot mass and slight increase in coolant temp. If allowed to complete, it will go until the soot mass is a negative number.

I believe the trigger for a regen is the pressure sensor going in and out of DPF. When it senses a high enough pressure difference is when it triggers a regen, assuming all parameters are present (engine temp, speed, etc.).

For me, this is roughly every 275miles, sometimes a little longer, rarely a little less. I usually reset my trip meter when it happens and look for it next when the meter gets close to 275miles.

 

[dbbyleo]

Good to know!

Update: Just got my car back from Audi. After several (5 times) failed attempts to regen and fix the P1A58 code. On the fifth try, the check engine light came on - P13D4 and P13D6. They couldn't tell how this was related to the P1A58 (NOx regen required), but replaced Cylinder 3 glow plug and pressure sensor. With the MIL off, they took it for a 6th attempt to regen. Finally, after putting on over 500 miles on my car, the DPF warning light went off.

I got the car back home. I wanted to check for myself so I hooked it up the VCDS. And sure enough... there are no malfunctions in 01 - Engine.

I checked the DPF stats...

Oil Ash Volume (241.1): 168ml (car has 148K miles) ... from what I this is really all just calculated on the mileage of the car.

Soot Load Calculated (241.2): 7.2g ... from what I understand, this is a good indicator of when I should take the car for a "burn drive" (ie drive in sport mode intentionally) for passive regen... i think I read at 20g the car will do an active regen (but not positive).

Particulate Filter Differential Pressure: 8mbar (@idle), 18mbar (@2000 rpm - stationary) ... from what I understand, this is really the indicator of how clogged your DPF is. Anything above 27mbar would indicated a very clogged DPF and by then, there may be all sorts of DPF/MIL light on and fault codes.

My problem is ... all these stats is this is related to the DPF, not the NOx cat/storage/converter. Does anyone know what/where in VCDS to get measurements of the conditions of the NOx?