Audi A4 Coolant Leak Points to Control Module Failure

As an Audi A6 2013 gasoline owner, I faced nearly identical symptoms. The coolant leak combined with overheating pointed to a faulty control module that incorrectly regulated the cooling system. After multiple car diagnostics sessions, we discovered a communication fault between the engine control unit and the cooling system sensors. The root cause was a combination of a wiring issue and corroded connections at the coolant temperature sensor. The control module was receiving incorrect temperature readings, causing the system to malfunction. The repair required: 1. Replacing damaged wiring harness 2. Installing new coolant temperature sensors 3. Updating control module software 4. Replacing corroded connectors This was classified as a serious repair since continued overheating could have led to engine failure. The software glitch in the control module also needed addressing to prevent future communication errors. Key warning signs were: Constant coolant loss, Temperature gauge fluctuations, Check engine light persistence, Control module error codes For proper diagnosis, the entire cooling system needs professional testing since symptoms can mimic a simple head gasket leak.

Thanks for sharing those details. I had similar issues with my 2011 A4 last winter. The connectivity issue between sensors and the control unit was indeed causing coolant system problems. After fixing the data link problems and replacing some corroded parts, everything works perfectly now. Would you mind sharing the total repair cost in your case? I paid around 850 Euro for the complete fix. Also, have you experienced any other cooling system or software glitch issues since the repair was done?

After bringing my A6 to the mechanic, the main CAN bus connectivity issue was actually less complex than initially feared. The diagnostic trouble code pointed to a damaged cable connection at the coolant sensor, which was causing the communication fault with the control module. The final repair bill came to just 95 Euro for fixing the faulty wiring connection. This was much less than your case since no major component replacements were needed. The mechanic found that cleaning and properly securing the connector resolved the control unit communication error. Since this repair 8 months ago, the cooling system has worked flawlessly with no temperature fluctuations or software glitches. The car diagnostics now show normal readings across all sensors. It seems the issue was purely related to that single degraded connection causing incorrect data transmission to the control module. Simple wiring issues can sometimes mimic more serious problems, which is why proper diagnostics are so crucial before replacing major components.

I finally decided to take my A4 to a specialized European car shop after dealing with the overheating issues. The mechanic found that my control module was getting faulty readings due to a corroded wiring harness near the coolant sensor. The car diagnostics revealed multiple communication fault codes in the CAN bus system. The repair process was straightforward once they identified the real problem. They replaced the damaged wiring, cleaned all the connectors, and updated the control module software. Total cost came to 850 Euro, which included parts and labor. The shop also found and fixed a small coolant leak at the water pump while they were at it. Its been 6 months since the repair, and the cooling system works perfectly now. No more check engine lights or temperature warnings. The data link between sensors and the control unit is stable, and coolant levels stay where they should. Definitely worth finding a shop that specializes in these types of electrical issues rather than just mechanical repairs.