Audi S7 Coolant System Pressure Causing ECU Glitches

As an S6 owner from 2010, I encountered nearly identical symptoms. The diagnostic trouble codes pointed to a control module failure affecting the coolant system management. The root cause was a damaged wiring harness near the coolant temperature sensor, creating intermittent data link errors between the engine control unit and cooling components. The CAN bus communication errors were causing the system to misread temperatures, resulting in improper pressure regulation. This explained both the temperature spikes and coolant loss. A complete diagnostic scan revealed multiple communication faults between modules. The fix required: Testing the complete sensor network, Replacing the damaged wiring harness, Recalibrating the control module, Verifying proper CAN bus communication This was indeed a serious issue that could have led to engine damage if left unaddressed. The software glitch triggering the check engine light was actually a symptom of the physical wiring problem, not the core issue. Recommend having a full diagnostic scan performed by a shop with Audi-specific testing equipment to properly isolate the failure point in the control system network.

Thanks for sharing that experience. My S7 problem sounds very similar, especially the temperature spikes and connectivity issues with the control module. Did you remember the total repair cost for the wiring harness replacement and recalibration? Also curious if you had any recurring issues with the CAN bus system after the fix was completed?

Great update, took my car to a certified shop last week and they confirmed the control unit communication error was indeed caused by a faulty cable connection. Total repair cost was 95 Euro to fix the damaged connector, which is way less than I initially feared. Since the repair, all connectivity issues have completely cleared up. The CAN bus system is now working perfectly, no more temperature spikes or coolant problems. The data link between modules is stable and the engine control unit is receiving accurate readings. The key was finding a technician who properly diagnosed the root cause instead of just treating symptoms. Unlike my experience with the previous workshop, this fix actually solved the underlying control module communication problem rather than just resetting error codes. A year later and everything is still working as it should. The diagnostic approach you are taking sounds spot-on based on my experience. Getting that proper initial diagnosis is crucial for these control system issues.

Thanks everyone for the helpful input. Finally got my S7 fixed after following the advice here. Took it to a specialist who immediately identified the faulty wiring causing the control module issues. The diagnostic trouble code scan revealed exactly what was suggested, damaged wiring creating communication faults between modules. The repair involved replacing a section of the harness and recalibrating the system. Total cost came to 850 Euro including parts and labor. Cooling system is now working perfectly. No more software glitches, temperature spikes, or coolant leaks. The data link between components is stable and all readings are normal. Such a relief to have it properly diagnosed and fixed after the previous misdiagnosis. Really appreciate the guidance that helped me understand the underlying issue. Would have spent way more money without zeroing in on the control module communication problem first.