SQ5 Temperature Sensor Causing Multiple System Failures

Having some experience with car repairs, I faced almost identical issues with my 2015 Q5 3.0T. The outside temperature sensor was definitely the culprit, causing similar problems with climate control systems and generating error codes. The main symptoms matched yours exactly, AC problems, frozen washer nozzles, and non-functioning mirror heating. After checking the vehicle temperature sensor connections, my mechanic found corroded wiring at the sensor plug. The temperature sensor replacement was straightforward, but accessing the wiring harness took some time. The total repair cost was 95 Euro, covering both parts and labor. The car temperature sensor calibration was included in this price. After the fix, all systems returned to normal operation. To help diagnose your specific case more accurately, could you share: Are you getting any specific error codes? When did these symptoms first appear? Have you noticed any other electrical issues? Does the temperature reading on your dashboard appear incorrect? This information would help determine if your SQ5 has the same sensor connectivity issue I experienced.

Thanks for the feedback. The fault codes are P0073 and P0072. Based on sensor diagnostics, they started appearing last week. Strange thing is, the temperature monitoring system shows -40C constantly, regardless of actual weather. Latest service was at 75538 KM where they also did a full electronic check, but these issues emerged afterward. The outside temperature sensor errors seem to be triggering other systems to malfunction as a safety measure. No other electrical problems noticed so far. The temperature readings are definitely incorrect which seems to match the symptoms you described with your Q5. Will have the temperature sensor replacement done and report back on the results.

Thanks for providing those details about the fault codes and sensor diagnostics. The constant -40C reading your getting is exactly what I experienced with my Q5 before the temperature sensor replacement. This is typically a telltale sign of a sensor malfunction where the system defaults to its lowest reading. The P0073 and P0072 codes confirm what we suspected, they specifically indicate an ambient air temperature sensor circuit high/low input. In my case, the sensor malfunction was causing these same codes, and like yours, my system defaulted to showing -40C. Since your service history shows a recent electronic check, the sensor issue likely developed afterward. This matches the typical failure pattern I experienced, these sensors often fail gradually before complete malfunction. One thing to note about the repair: make sure they check the entire wiring harness during the temperature sensor replacement. In my repair, they found additional corrosion further along the wiring that needed addressing to prevent future issues. Would be interested to hear how the repair goes and if it resolves all the connected systems like it did in my case. The AC, washer nozzles, and mirror heating should all return to normal operation once the new sensor is properly calibrated.

Thanks everyone for the insights. Just had the repair done and wanted to close the loop. The vehicle temperature sensor replacement fixed everything, all systems are now working perfectly. The sensor malfunction was indeed causing all those issues. They found significant corrosion around the outside temperature sensor wiring, just as suggested. Total cost came to 110 Euro including sensor calibration and harness inspection. The temperature readings are now accurate, AC works normally, and the washer nozzles operate properly even in cold conditions. Mirror heating also functions as intended. The error codes P0073 and P0072 have cleared and haven't returned. For anyone else experiencing similar symptoms with constant -40C readings and multiple system failures, definitely check the temperature sensor connections first. The repair was straightforward once properly diagnosed.