SQ8 Diesel DPF Issues Cause Power Loss & Black Smoke

Had the exact same symptoms on my 2017 SQ7 TDI last winter. Have some experience with DPF issues and emission control systems from maintaining several diesel vehicles. The main issue turned out to be a faulty exhaust back pressure sensor. The defective pressure sensor was causing incorrect readings, which affected the DPF regeneration cycle and led to those exact symptoms, reduced power, black smoke, and exhaust smell. Took it to a workshop where they ran a diagnostic test which confirmed the sensor malfunction. The repair involved replacing the pressure sensor and performing a forced DPF regeneration to clear any built-up soot. Total cost was 245 Euro including parts and labor. Since the fix, the car has been running perfectly with no warning lights or performance issues. The DPF regeneration cycles are now working as intended. Before suggesting more specific solutions, could you provide: Any diagnostic codes youre getting, When was your last DPF regeneration, Has the car been mainly used for short trips or highway driving, Have you noticed any unusual fuel consumption patterns This information would help determine if youre facing the same root cause or if theres another underlying issue with your emission control system.

Latest service at 80497 KM and having similar symptoms as described. The dealer replaced my DPF pressure sensor last week but the warning lights returned after a few days of normal operation. When they checked again, they found accumulated soot despite successful forced DPF regeneration. Based on my experience, the constant reduced power mode and recurring particulate filter warnings suggest there might be additional issues beyond just the sensor. Perhaps fuel injectors or EGR valve problems causing excessive soot buildup in the DPF system. Could there be something else causing these persistent DPF regeneration failures even with a new pressure sensor installed?

Thanks for the update on your SQ8 situation. After having my pressure sensor replaced on my SQ7, I also experienced similar recurring issues, which turned out to be more complex than initially diagnosed. In my case, the root cause was actually a failing EGR valve that was causing excessive soot production, overwhelming the DPF system even after successful regeneration cycles. The faulty EGR valve was contaminating the intake system with carbon deposits, leading to constant reduced power modes and emission control warnings. The complete fix involved: Cleaning the EGR valve and intake manifold, Replacing the EGR valve assembly, Performing another DPF regeneration, Cleaning the exhaust system components Total repair cost was around 890 Euro, but it permanently resolved the recurring issues. The car has been running smoothly for 30000km since, with normal DPF regeneration cycles and no warning lights. Based on your symptoms, I suggest having the workshop check: EGR valve functionality and carbon buildup, Fuel injector spray patterns, Boost pressure readings, Complete exhaust system for any restrictions These components often work together in causing DPF issues, and replacing just the pressure sensor might not address the underlying problem causing excessive soot production.

You should have your fuel injectors tested too, my exhaust system problems turned out to be more complex than first thought. After getting a second opinion, the mechanic found that two of my fuel injectors were partially clogged, causing uneven fuel spray patterns. This was creating excess soot that kept overwhelming the DPF, even after sensor replacement and regeneration. The constant reduced power mode makes sense now, the diesel engine management system was detecting the poor combustion and restricting performance to protect the emission control components. My DPF pressure readings were all over the place because of the uneven soot buildup from those faulty injectors. I decided to have all injectors cleaned and tested, plus a full exhaust system inspection. The total bill came to 1100 Euro but it was worth it, no more warning lights or performance issues for the past 5000km. The DPF regeneration cycles are now completing normally. Let me know what your workshop finds regarding the injectors. Based on our similar symptoms, I suspect they might discover injection issues beyond just the DPF sensors we both had replaced.