RS7 Water Sensor Issues Causing Engine Problems

I had a very similar electrical fault on my 2016 RS6. With some experience working on various auto electronics, I initially tried basic diagnostics but quickly realized this needed professional attention. The malfunction indicator was showing sensor-related codes, and the engine was running inconsistently. After sensor testing at my regular workshop, they discovered the water sensor had a faulty connection. The issue was not the sensor itself, but rather corroded plug connections that were causing intermittent electrical faults. The fix involved cleaning the connections and replacing some damaged wiring, total cost was 95 Euro. Since then, no more engine management system warnings or rough running issues. To provide more specific advice for your case, could you share: Current mileage, Any recent work done on the car, Whether the issue started suddenly or developed gradually, If the problem occurs more when the engine is cold or warm, Which specific fault codes are showing This would help determine if your issue matches what I experienced with the water sensor connections.

Last service was at 142000 KM, currently at 143080 KM. The issue started developing gradually over the past few weeks. The check engine light initially flickered before staying on permanently. The sensor fault seems more pronounced when the engine is cold. I am getting fault code P0193, which points to a fuel rail pressure sensor issue. Wondering if this could be related to the water sensor problem, since I have noticed the engine running particularly rough on cold, damp mornings. Your insight about the corroded connections is helpful, might be worth checking the wiring harness for similar issues. Could anybody recommend specific sensor testing procedures before I take it to a shop? Want to be better informed about potential issues when discussing repairs.

Having gone through similar symptoms with my RS6, those cold morning issues you mention really resonate with my experience. The moisture sensor readings on damp mornings were definitely part of the puzzle in my case. The P0193 code you are getting actually makes sense in this context. While it points to the fuel rail pressure sensor, in my case the faulty water sensor connections were causing cascade failures in the engine management system, triggering multiple sensor readings to go haywire. Before taking it to the shop, here is what worked for me with sensor testing: Check all visible sensor connections for corrosion, Use a multimeter to test the voltage at the water sensor connector, Listen for the fuel pump prime when turning the key, Monitor the live data stream for irregular sensor readings The fact that your issues developed gradually, like mine did, suggests an electrical degradation rather than sudden sensor failure. The correlation with cold starts and damp conditions further supports this. Since you are only 1080 KM past your last service, I would also check if any work was done near the wiring harness that could have disturbed connections. My repair was straightforward once the root cause was identified, though costs can vary depending on the extent of corrosion found during diagnostics.

Thanks for sharing those details about your experience with the RS6. The timing seems very similar, as does the issue with cold starts and connection problems. Mine has definitely gotten worse during the recent wet weather. I will try checking the sensor connections and wiring harness as suggested. The electrical fault seems the most likely culprit given the gradual onset and the way it acts up in damp conditions. I have a multimeter so I will test the voltage readings at the water sensor connector points before booking it in for repairs. The shop did replace some components near the main wiring harness during the last service, so your point about disturbed connections makes sense. I will specifically ask them to check for any moisture sensor or other sensor-related issues that could have developed since then. Appreciate the detailed troubleshooting steps. Will get started with the basic sensor testing and report back once I have more findings or get it properly diagnosed at the shop. Really hoping it is just corroded connections rather than a full sensor malfunction in the engine management system.