Audi TT Flashing CEL Linked to Faulty O2 Sensor

Had a similar situation on my 2013 Audi S5 last winter. The check engine light started flashing while the oxygen sensor heater element was failing. The symptoms matched exactly, increased fuel consumption and rough idle. After sensor testing confirmed the diagnosis, it required replacing the entire oxygen sensor unit in the exhaust system. The repair was straightforward but accessing the sensor proved tricky due to its location in the air-fuel ratio monitoring section. This is a serious issue that needs prompt attention since: It affects engine performance, Increases fuel consumption significantly, Can damage the catalytic converter if left unfixed, Impacts emissions control The job took about 2 hours in total. A certified mechanic should be able to properly diagnose and replace just the faulty oxygen sensor without suggesting unnecessary additional repairs. The part itself is readily available through official channels. Make sure they perform proper sensor testing before and after installation to verify the repair was successful. Ask for the old part back, a reliable shop will have no issue with this request.

Thanks for confirming my suspicions about the oxygen sensor. Your experience mirrors what I am seeing with my TT, especially the rough idle and higher fuel usage. The check engine light has been a constant reminder something is wrong with the air-fuel ratio monitoring. Getting that part location detail is helpful since I was worried about accessibility in the exhaust system. Would you mind sharing what the total repair cost was for you? Also curious if youve had any other sensor issues pop up since the repair was done.

Got my 2013 S5 back from the mechanic last week after dealing with that oxygen sensor problem. You will be glad to hear that after fixing a faulty cable connection to the sensor heater unit, everything is running perfectly now. The entire repair came to 95 Euro, which was a relief since I initially worried it might need a complete sensor replacement. The rough idle and fuel consumption issues disappeared right after the repair. During sensor testing, they discovered it was just a damaged wire connection causing the heater element failure, not the entire sensor being faulty. This type of repair is much simpler than replacing the whole unit in the exhaust system. Have not seen any check engine light warnings since then and no other car components have shown any problems. The fuel economy is back to normal too. If your issue turns out to be similar, the repair should be straightforward for any competent mechanic familiar with these systems.

I finally got my TT fixed and wanted to share my experience. After checking several repair shops, I found one that specialized in sensor diagnostics. The mechanic immediately identified the faulty oxygen sensor in the exhaust system and showed me exactly where the problem was. The repair took about 2 hours, just as expected. The final cost was 320 Euro, including parts and labor. The check engine light disappeared right after fixing it, and my fuel consumption dropped back to normal levels. They did thorough sensor testing afterward to ensure everything was working correctly. I got to keep the old part and could clearly see the damage to the heater element. No other repairs were needed, and the mechanic was upfront about the whole process. Its been two weeks now, and the car runs perfectly, no warning lights or rough idling anymore.