Teana engine overheats communication error

Sounds like a tricky one. A control unit communication error could stem from a few things. Are you able to check if all the cable and plug connections to the control modules are properly seated? Sometimes a loose connection can cause intermittent communication and trigger those symptoms. Also, does your scanner specify which control unit is having the communication problem?

I'll check the connections. Where exactly are these control units located? And no, the scanner doesn't specify a particular unit, just a general communication error.

Okay, lacking a specific unit makes it tougher. Unfortunately, pinpointing all of their locations is difficult without specific knowledge of your car's configuration; there are often several modules spread throughout the vehicle. Given the overheating and coolant issue alongside the communication error, it's still likely a connection issue but could also be a faulty module or even a CAN bus problem. If you're not comfortable digging around, I'd advise taking it to a workshop. They've got the tools and experience to properly diagnose it.

Okay, I will check the connections I can easily access, but it sounds like a workshop visit is unavoidable. Thanks for the advice. The defective cable/plug connection was found and repaired; total cost 95€.