SQ5 DPF Failure Causing Power Loss and Black Smoke

Had similar issues on my 2017 Audi A6 3.0 TDI. The exhaust back pressure sensor was showing erratic readings, triggering reduced power mode and DPF warnings. These symptoms match exactly what you describe, black smoke during acceleration and that distinctive diesel exhaust smell indicate restricted flow in the exhaust system. The low pressure readings at the DPF typically point to either a faulty sensor or clogged particulate filter. In my case, diagnostic testing revealed the sensor itself was defective, not the DPF. This is actually preferable since sensor replacement is less complex than DPF work. The repair involved: 1. Complete sensor unit replacement 2. Exhaust system pressure test 3. ECU fault code reset 4. Test drive to confirm normal operation While not a minor issue, sensor failure is common on these diesel engines and far less serious than internal DPF damage. The repair restored proper power delivery and eliminated all warning lights. Would recommend having a specialized diesel workshop perform proper diagnostics before replacing parts. The symptoms you describe are very specific to either sensor malfunction or DPF restriction.

Thanks for sharing those details about your A6 repair. The symptoms you described with the exhaust system and reduced power mode match my SQ5 situation perfectly. I will follow your advice and get it checked at a diesel specialist. Do you remember roughly what you paid for the sensor replacement and testing? Also curious if you had any DPF issues pop up since the repair was done? Having the proper diagnostic work first definitely makes sense versus just throwing parts at the problem. The pressure sensor route sounds promising since my diesel engine symptoms are so similar to what you experienced.

Thanks for asking about the follow-up. Yes, I can confirm the exhaust pressure sensor repair on my A6 has completely resolved the issues. The total cost was 245 Euro for parts and labor, which included diagnostics, sensor replacement, and testing. The emission control system has worked flawlessly since fixing the faulty pressure sensor. No more reduced power mode, warning lights, or DPF issues in over 40000 km of driving. The black smoke and strong diesel smell disappeared completely after the repair. A proper diagnosis was key, the exhaust system pressure test clearly showed the sensor was providing incorrect readings to the engine management system. Once replaced, the DPF functioned normally again during regeneration cycles. This repair cost significantly less than a full DPF replacement would have, and resolved all the symptoms. The engine now performs as intended with normal power delivery and proper emission control.

I took my SQ5 to a reputable diesel specialist last week following the advice here. The diagnostic testing confirmed a faulty exhaust pressure sensor was causing my issues. The repair process went smoothly, they replaced the sensor, performed a full system pressure test, and cleared the fault codes. Total cost came to 290 Euro, which was a relief compared to what a DPF replacement would have cost. The emission control system is now working perfectly. No more black smoke, diesel smell, or reduced power warnings. The engine runs strong again and all warning lights have stayed off. Really glad I got proper diagnostics done first instead of rushing into major repairs. Will definitely stick with this shop for future diesel engine work. Their thorough testing approach saved me from unnecessarily replacing the entire DPF. The low pressure sensor was clearly the root cause of all my symptoms.