Audi S5 Fuel Sensor Issue Causing Engine Stalls

I had a similar issue with my 2021 Audi S4, and I have some experience working on these cars. The symptoms you describe match exactly what I encountered, stalling at idle and check engine light. In my case, a faulty sensor in the fuel tank was triggering false readings, but the actual fix was surprisingly simple. The level sensor fault was caused by a blown fuse. The repair took about 30 minutes at the workshop and cost 52 Euro for diagnostics and fuse replacement. Before jumping to replace the entire fuel sensor, definitely have them check the fuse box first. These fuel level sensor issues can sometimes be traced back to electrical problems rather than the sensor itself. To provide more specific guidance: Which engine variant does your S5 have? Have you noticed any unusual fuel gauge behavior? Does the stalling happen more frequently with a low fuel tank? This information would help determine if your issue matches what I experienced or if you might be dealing with a different fuel system problem.

Thanks for the detailed response. My S5 has covered 160075 KM since last service. After checking the fuse box as suggested, the problem persists. The fuel gauge fluctuates out of nowhere and the car stalls more frequently when the fuel tank is below quarter full. The car sensor issues get worse in stop-and-go traffic. The car dashboard also shows inconsistent fuel readings. Multiple fault codes point to the level sensor. Would replacing the entire fuel tank sensor assembly be the next logical step?

Thanks for those additional details, this definitely helps clarify the issue. After my fuse replacement didnt work, I ended up having to replace the entire fuel tank sensor assembly in my S4. The symptoms you describe, especially the fluctuating fuel gauge and increased stalling with low fuel levels, are identical to what I experienced. The car electronics were constantly getting incorrect readings from the faulty sensor, which caused the engine management system to miscalculate fuel delivery. The repair involved: 1. Draining the fuel tank 2. Removing the old sensor assembly 3. Installing the new unit 4. Clearing the fault codes Total cost was around 450 Euro, including parts and labor. The fuel system started working perfectly after the replacement, and the stalling issues completely disappeared. Given the high mileage and matching symptoms, replacing the fuel tank sensor assembly is likely the right solution. Just make sure the workshop performs a complete diagnostic test first to confirm no other fuel system components are affected. Since you mentioned the problems worsen in stop-and-go traffic, monitoring the fuel pressure during these conditions might also be worthwhile to rule out pump issues.

Thank you for the thorough explanation. Based on your experience, I will proceed with replacing the fuel tank sensor assembly. The symptoms align perfectly, especially the erratic fuel gauge behavior and stalling issues in stop-and-go traffic. The car dashboard warnings and multiple fault codes also point in this direction. 450 Euro for parts and labor seems reasonable considering the complexity of accessing the fuel tank. Will schedule the repair next week and make sure they do the complete diagnostic test you suggested to rule out any fuel pump problems. Getting this fixed should resolve both the sensor fault warnings and the stalling issues. Will update once the repair is complete in case anyone else runs into similar fuel level sensor problems with their vehicle. Thanks again for helping narrow down the exact issue.