S4 DPF Sensor Issues Causing Regen and Smoke Problems

The symptoms match what I experienced with my 2020 Audi A6 TDI. The exhaust back pressure sensor failure caused similar issues, excessive smoke, failed DPF regenerations, and constant warning lights. After proper diagnosis, it turned out the sensor was not just defective but had accumulated carbon deposits, affecting engine performance and vehicle emissions readings. The repair required: 1. Complete sensor replacement 2. DPF cleaning 3. ECU recalibration for the new sensor 4. Full emission control system check This was a serious issue that needed immediate attention, as faulty readings can lead to: Incorrect fuel injection timing, Incomplete DPF regeneration cycles, Potential engine damage if left untreated, Failed emission tests The repair process took about 6 hours total. Since fixing it, the exhaust system has performed flawlessly with no more regeneration failures or smoke issues. Would strongly recommend having a certified diesel specialist handle this, as proper calibration is crucial for the system to work correctly.

Thanks for sharing your experience, really helps confirm my suspicions about the pressure sensor being the culprit. My S4 shows the exact same symptoms with the DPF regen failures and smoke. How has your repair held up long-term? Would be great to know what you paid for the whole job, just so I have a ballpark figure when talking to shops. Also curious if youve had any other emission control problems pop up since the fix?

Glad to provide an update. The auto repair work on my A6 has proven totally reliable, its been running perfectly since getting the exhaust back pressure sensor replaced. The 245 Euro I paid for the sensor fix was money well spent, considering how critical this component is for proper emission control. No other exhaust system problems have surfaced in the months since. The vehicle emissions are now normal, with no more warning lights or smoke issues. The DPF regeneration cycles work as they should, and the back pressure readings stay consistent. One tip from my experience: once fixed, regular driving patterns that allow complete regeneration cycles help prevent future pressure sensor issues. Short trips can lead to carbon buildup affecting sensor readings again. The repair shop did a thorough job with calibration, which I think made the difference in getting lasting results. Worth making sure whoever does the work includes proper sensor calibration in their service.

Thanks everyone for the helpful feedback. Finally got my S4 fixed last week and wanted to share how it went. Found a specialized diesel workshop that really knew their stuff. The vehicle diagnostics confirmed the faulty back pressure sensor, just as suspected. Total repair came to 280 Euro including: New pressure sensor, System cleaning, Full calibration, Diagnostic scan The car runs like new now, no more smoke, warning lights are gone, and engine performance is back to normal. DPF regeneration cycles work perfectly. Huge relief to have it sorted properly. The mechanic showed me the old sensor, it was completely gunked up with carbon. They also gave some good advice about avoiding too many short trips to prevent future buildup. Really appreciate all the guidance here. Helped me go into the auto repair shop knowing exactly what to expect. Money well spent to get the emission control system working right again.