Audi A2 Water Sensor Causing Rough Engine + MIL Light

Had similar symptoms on my 2008 Audi A3 2.0 TDI. The electrical fault turned out to be a corroded connection at the water sensor plug, causing inconsistent readings and rough engine performance. Car diagnostics showed multiple error codes initially, all pointing to sensor faults. After thorough sensor testing, the mechanic traced the issue to water damage at the connector. Moisture had entered through a damaged seal, leading to corrosion of the terminals. The fix required cleaning the connector, replacing the damaged seal, and applying dielectric grease to prevent future issues. While not a major repair, leaving it unaddressed could have led to more serious problems like fuel system damage or engine misfires. The water sensor plays a crucial role in detecting water in the fuel system, so proper function is essential for engine protection. Based on the symptoms described, checking the sensor connections should be the first step before replacing any components. Consider requesting a complete sensor testing report to verify the diagnosis. Water sensor issues often manifest exactly as described, rough running and warning lights.

Thanks for sharing your experience. My A2 had almost identical symptoms, and you are right about the water sensor being the culprit. The mechanic did a thorough car diagnostics check and found corrosion on the sensor contacts, just like in your case. Did you remember how much the repair cost you? Also, curious if the malfunction indicator came back on or if you experienced any related sensor faults since the fix? Would be helpful to know for budgeting and to understand if this is likely a one-time fix or something that needs regular maintenance.

After getting the repairs done last month, the moisture sensor issue was completely resolved on my A3. The fix was straightforward, the mechanic cleaned and repaired the cable connection, which cost 95 Euro including labor. The malfunction indicator has stayed off since then, and the engine runs smoothly again. The car diagnostics showed no further sensor faults after the repair. Based on what the mechanic explained, these issues typically dont reoccur if properly fixed with the right protective measures. They applied some protective coating to prevent future corrosion, which was included in the repair cost. Regular maintenance of sensor connections isnt typically needed, but its worth having the fuel system checked during routine services to catch any potential issues early. The water sensor should work reliably for years now that the connection has been properly sealed.

I took my A2 to the mechanic last week and can now share my resolution. The water sensor repair was exactly what I needed. They found extensive corrosion on the contacts, cleaned everything thoroughly, and applied a protective coating. Total cost came to 120 Euro including a full sensor testing procedure. The car runs perfectly now, no more rough engine performance or warning lights. Really glad I got it sorted quickly before it could cause any fuel system damage. The sensor issue was indeed identical to what you experienced, and getting a second opinion through this forum helped confirm I was making the right call. What a relief to have this fixed properly. No sensor faults since the repair, and the mechanic assured me this should be a long-term solution. Makes me more confident about future warning lights too, knowing when to trust the initial diagnosis can save a lot of worry.