VW Tiguan Coolant Loss & Overheat: ECU Link Failure

I had similar issues with my 2015 VW Passat TDI. The symptoms matched exactly, engine overheating, coolant loss, and persistent check engine warnings. After visiting a specialized workshop, they identified a faulty CAN bus connection between the engine control unit and the cooling system control module. The root cause was a damaged wiring harness connector that disrupted the communication between modules. This created incorrect readings of coolant temperature, causing the system to malfunction. The connectivity issue meant the cooling fans werent activating at the proper times. This type of communication fault requires specific diagnostic equipment to properly identify. A standard OBD scanner might show generic cooling system codes, but pinpointing the exact control module communication problem needs more advanced tools. The repair involved replacing the damaged connector and recalibrating the control units. While not the most expensive fix, diagnosing the exact issue was crucial. A shop with manufacturer-specific diagnostic capabilities is essential for these types of electronic control system problems. Consider having the CAN bus network tested specifically. When the control modules cant communicate properly, it often manifests as cooling system issues, even when the mechanical components are fine.

Thanks for sharing that detail about your Passat. Your experience sounds exactly like what happened to my Tiguan last summer. The specialized workshop also found communication issues between the control modules in my case. Do you remember roughly how much the diagnostic and repair ended up costing? Also curious if youve had any related issues pop up since getting it fixed? I had mine repaired about 6 months ago but always like to hear about long-term reliability after these kinds of data link problems.

Great news, since having my Passat checked at the workshop, the control module communication error hasnt returned at all. The diagnostic trouble code they found was related to a damaged connector affecting the CAN bus system. Total repair cost came to 95€, which covered fixing the cable connection and testing the component. The software glitch symptoms completely disappeared after they repaired the connectivity issue. No more engine overheating or coolant problems in the past 18 months. The car diagnostics they ran after the fix confirmed all systems were communicating properly again. Sounds like both our vehicles had nearly identical control module problems, but once properly diagnosed and fixed, the solution was pretty straightforward. The key was having the right diagnostic equipment to pinpoint the exact communication fault in the system.

Thanks for the helpful responses. I finally took my Tiguan to a specialized VW shop last week. Their advanced diagnostic equipment found a data link issue between the coolant temperature sensor and the main control unit. The mechanic showed me where the wiring had deteriorated, causing the communication fault. Repair cost was 180€ including parts and labor. They also performed a full system diagnostic to ensure no other CAN bus connectivity issues were present. Been driving for about a week now and the engine temperature stays perfectly normal. No more coolant loss or warning lights. Really glad I switched to a shop with proper diagnostic tools, saved me from potentially replacing parts that weren't actually broken. Lesson learned about going to specialists for these complex electronic problems rather than general repair shops. The cooling system is working exactly as it should now.