S4 Temperature Sensor Chaos Disrupts Multiple Systems

I had a very similar issue with my 2017 S5. With limited experience working on car electronics, I decided to have it checked by a workshop rather than attempting DIY repairs. The vehicle temperature gauge was showing incorrect readings, affecting multiple temperature-dependent systems. The workshop diagnosed a faulty wiring connection to the main temperature sensor. The temperature monitoring system relies heavily on proper connections, and in my case, corrosion had damaged the plug connecting to the sensor. The fix involved cleaning the connection points and replacing the damaged wiring harness near the temperature sensor. Total cost was 95 Euro including labor. Since the repair, all temperature-dependent systems have been working perfectly. Before suggesting specific solutions, could you provide: Current temperature sensor readings on your display, Whether the issues started gradually or suddenly, Any recent work done near the front bumper where the sensor calibration might have been affected, Specific error codes from your diagnostic scan This information would help determine if your issue matches what I experienced with the sensor connection problem. Remember that multiple systems rely on accurate temperature sensor data, so a single fault in the main sensor or its wiring can indeed cause widespread issues.

Last service was at 7500 KM. The sensor diagnostics showed both ghost readings and complete signal loss from the vehicle temperature sensor. The readings would fluctuate wildly between -40C and +80C within minutes. Our issues appear quite similar, especially regarding multiple affected systems. After reading about your experience with wiring problems, I checked the connection points around the temperature sensor housing and noticed some signs of water ingress. This could explain the erratic sensor behavior and system-wide temperature gauge malfunctions. Will definitely have the wiring inspected before replacing the entire sensor module. The gradual nature of the sensor malfunction does align with potential corrosion damage rather than sudden electronic failure. Did your repair shop mention any specific preventive measures to avoid future sensor issues?

As I mentioned in my earlier response about my S5 repair, protecting the wiring connections is crucial for long-term reliability of the temperature monitoring system. The repair shop actually recommended applying a dielectric grease to the sensor connections after cleaning them, which helps prevent future corrosion. Those extreme temperature readings you describe (-40C to +80C) are very similar to what I experienced when my wiring was compromised. The temperature sensor replacement itself wasnt necessary in my case, and based on your description, you might also just need the wiring connections cleaned and protected. Since youve spotted water ingress around the sensor housing, thats likely the root cause. On these models, water can slowly seep in through tiny cracks in the protective covering, gradually corroding the vehicle temperature sensor connections. The erratic readings are a classic symptom of this issue. One thing to note, after my repair, the workshop applied a special sealant around the sensor housing to prevent future water infiltration. The total sensor replacement cost would have been around 280 Euro, but the wiring fix was much more economical at 95 Euro. Given the similar symptoms and progression of issues, Id recommend having your shop focus on the wiring and connections before considering a complete temperature sensor replacement.

Thanks for all the feedback on my temperature sensor issues. The symptoms youve described match my situation perfectly, especially the part about water damage affecting the connections rather than the sensor itself being faulty. Ive booked the car in next week for inspection and repair. Given what youve shared about your experience, Ill specifically ask them to: Check the wiring connections around the outside temperature sensor, Clean any corrosion from the sensor contact points, Apply dielectric grease to protect the connections, Inspect and reseal the sensor housing to prevent future water ingress The sensor diagnostics match exactly what you experienced, so Im hopeful this will be a wiring fix rather than needing full sensor replacement. The difference between 95 Euro and 280 Euro is significant, and it makes sense to try the simpler fix first since the temperature monitoring symptoms point to connection issues. If the temperature sensor malfunction continues after addressing the wiring, Ill update the forum with the outcome. Thank you for helping narrow down the likely cause, this will save time at the workshop since they can focus on the wiring connections first.