Audi A1 Cooling System Failure Linked to Control Unit

Having some experience with car repairs, I faced nearly identical symptoms with my 2018 Audi A3. The initial signs matched yours exactly, overheating engine, check engine light, and coolant leaks. After investigating, it turned out to be a wiring issue affecting the cooling system control module. The connection between the ECU and cooling system sensors had deteriorated, causing incorrect temperature readings and system malfunctions. The workshop diagnosed a connectivity issue using professional car diagnostics equipment. They found damaged wiring and a loose plug connection at the control module. The repair involved replacing the damaged wiring harness and securing proper connections to the data link components. Total cost was 95 Euro, which included diagnostics and the repair work. The fix completely resolved the overheating problems and the check engine light hasn't returned since. To provide more specific advice for your case, could you share: Have you noticed any correlation between the overheating and specific driving conditions? What error codes showed up in the diagnostic scan? Does the temperature gauge show consistent readings or does it fluctuate?

Thanks for the detailed reply. According to my service records from last month at 139877KM, the workshop already checked and confirmed all cooling system connections were tight and properly seated. The diagnostic trouble code I got was P0597, which points to a thermostat heater control circuit issue. The temperature readings are erratic, jumping between normal and high with no clear pattern. The CAN bus diagnostic also showed communication errors between the engine control module and the thermostat controller. I am thinking this might indicate a software glitch rather than just a physical wiring issue, but wanted to confirm if anyone else resolved similar symptoms through a control module update.

Thanks for providing those additional details. When my A3 showed those symptoms, I initially thought it was just the wiring too, but after seeing the P0597 code like yours, it turned out more complex. The erratic temperature behavior you describe matches what I experienced, the communication fault between modules was causing the thermostat to receive inconsistent commands. In my case, while the physical connections were good, a software glitch in the control module was misinterpreting the temperature sensor data. The permanent fix required two steps: 1. Control module software update to address the communication fault 2. Reset and recalibration of the thermostat controller After the software update, the car diagnostics showed normal communication between modules. The repair shop mentioned these thermostat control circuit issues often stem from outdated module programming rather than hardware failures. Total repair time was about 2 hours and cost 180 Euro. Since then, temperature readings have been steady and no more coolant leaks or overheating issues. Have you checked if there are any pending software updates for your specific model year control module?

Thank you for the clarification. My dealership mentioned software updates being available but did not specifically connect them to the thermostat control issues. Your experience really helps confirm my suspicion about the control module needing an update to resolve these symptoms. The software glitch theory makes sense given that all physical connections were verified during the last service. The diagnostic trouble code P0597 and erratic CAN bus communication patterns match your situation exactly. The data link errors between the engine control unit and thermostat controller seem to point clearly to a programming issue rather than hardware failure. I will schedule an appointment to have the control module software updated and thermostat controller recalibrated. The cost estimate of around 180 Euro seems reasonable for resolving this specific fault. I appreciate the detailed breakdown of the repair process and confirmation that the fix resolved similar symptoms permanently in your case.