V90 Overheating and Communication Error

Greetings! I once wrestled with a similar gremlin on my old 2018 Audi A4. The symptoms you describe – overheating, check engine light, and coolant issues – strongly suggest a communication fault within the car's network. In my case, the culprit was a corroded connector on the data link connecting the ECU to the temperature sensors. The diagnostic codes pointed all over the place until I started inspecting the wiring harness. Have you had a close look at the cable and plug connections of the control unit?

Thanks for the quick reply! When you say 'data link connecting the ECU to the temperature sensors', do you mean the main wiring harness going into the ECU, or are there specific connectors I should be looking for? Also, how did you pinpoint the corroded connector? I'm not sure where to start looking, to be honest.

Indeed. By 'data link', I am referring to the wiring harness that facilitates communication between the Engine Control Unit (ECU) and various sensors, particularly the temperature sensors in your cooling system. Given the 'control unit communication error' flagged by your OBD scanner, it's highly probable that a defective cable or plug connection is the root cause. Pinpointing corrosion required meticulous inspection, a multimeter to check for continuity, and a wiring diagram specific to my Audi model. Considering the potential complexity and the risk of exacerbating the issue, I would strongly recommend seeking professional assistance from a trusted Volvo workshop. This issue could cascade and cause more severe damage to your Volvo V90.

Just wanted to thank you for your advice! I took the V90 to the shop, and it turned out to be a corroded connector, just like you suspected. They cleaned it up and replaced a short section of the wiring. The total cost was 95€. Everything seems to be running smoothly now!