VW Suran Coolant Leak & ECU Fault Requires Expert Fix

Had similar issues with a 2009 VW Golf GTI. The symptoms matched exactly, coolant problems, overheating, constant check engine light. Initial diagnostics pointed to a control unit malfunction. The root cause turned out to be a damaged wiring harness connecting to the engine control module. The CAN bus system was not properly communicating with the cooling system sensors due to corroded pins in the main connector. This caused incorrect temperature readings and system malfunctions. This required specialized diagnostic equipment to properly identify the data link issues. A standard OBD reader could only show generic fault codes. The repair involved replacing the damaged wiring section and connector, plus recalibrating the control module. Given the symptoms described, recommend having a VW specialist check the communication fault between the control unit and cooling system sensors. The software glitch causing the check engine light likely stems from corrupted signals due to wiring issues, not necessarily a failed module. This was a serious repair that required specific VW diagnostic tools and expertise. Generic repairs would likely not solve the underlying communication system problems.

Thanks for sharing your experience with the GTI wiring issues. My situation ended up being very similar, the car diagnostics also revealed problems with the control unit communication. The mechanic found corroded wiring affecting the CAN bus signals, which explained the erratic cooling system behavior. How much did you end up paying for the full repair? Has the fix held up without any new software glitches or communication faults showing up since then? Just want to compare costs and make sure this is truly fixed for good before wrapping up at my shop.

The wiring repair and connector replacement for my GTI came to 95€ total, which seems reasonable considering the specialized diagnostic work needed. Since having the control module communication error fixed, the car has run perfectly with no connectivity issues or coolant problems. The data link between the control unit and sensors is now working as intended, no more error codes or check engine lights. The investment in proper car diagnostics and repair by a qualified technician was worth it to permanently resolve the communication fault. The key was addressing the root cause with the corroded wiring rather than just clearing codes or making temporary fixes. Quality repairs to the control module connections tend to be a long-term solution when done correctly. Going on several months now with zero symptoms returning.

I finally got the repair done and what a relief, turns out my mechanic found almost the exact same wiring problems you described. The car diagnostics showed the control module wasnt getting proper signals due to damaged wiring in the CAN bus system. They charged me 120€ for the full repair including parts and labor. The mechanic showed me the corroded connector they replaced and explained how it was disrupting communication between the control unit and engine sensors. Since the repair three weeks ago, no more coolant issues or check engine lights. The communication fault seems completely resolved. Really glad I had this properly diagnosed instead of trying cheaper fixes that wouldnt have solved the underlying control module problems. Having a shop with the right diagnostic equipment to trace these data link issues made all the difference. Thanks again for helping point me in the right direction with your similar experience. The repair was definitely worth the investment to fix it right the first time.