Mercedes A Klasse diesel overheating communication fault resolved

Control unit communication fault on a 2012 A Klasse diesel sounds familiar. Overheating and coolant spills are textbook symptoms. Have you checked the wiring and plugs connected to the engine control unit itself? A bad connection there could definitely cause a communication breakdown, leading to incorrect fan operation and weird sensor readings. Maybe it's just a connectivity issue. Is the error code specific, can you specify the error code to narrow it down?

Thanks for the quick response! I haven't specifically checked the ECU wiring itself, I was focusing on the sensors. Where is the ECU located on this model? Is there a specific plug or wire that is a common culprit for these connectivity issues?

The ECU on your A Klasse is usually located in the engine compartment, often near the battery or behind the front bumper on either side. Unfortunately, there isn't one specific plug known for failing; it's more about corrosion or damage to the wiring harness in general. Given the overheating, the communication fault code, and the coolant loss, it really does point to a potential wiring issue affecting sensor readings. It would be best to get the car to a workshop or experienced technician to inspect the wiring harness thoroughly. Continuing to drive it with an overheating engine could cause further damage.

Thanks a lot, I appreciate the help! I took it to a mechanic, who had the same idea. Turns out it was a corroded plug on one of the sensors causing a communication fault. Total cost 95€ including diagnostics. Good call!