Skoda Roomster Overheating and Check Engine Light

Overheating, coolant loss, and a check engine light on your 2008 Skoda Roomster diesel is definitely concerning. The symptoms you are describing do point towards a possible communication fault within the car's electronic system. When the engine control module (the 'control unit' as you called it) cannot communicate properly with other components over the CAN bus (Controller Area Network – essentially the car's internal data network), it can lead to all sorts of issues. Is the check engine light constantly on, or does it flash? Does the overheating occur consistently, or only under certain conditions, such as when idling or driving uphill?

Thank you for your reply. Regarding the check engine light, it is constantly illuminated. The overheating seems to occur more frequently when the engine is under load, such as during acceleration or when climbing hills. Could you elaborate more on the CAN bus and its relation to the control module?

The CAN bus is the communication network that allows various electronic control units (ECUs), like the engine control module, transmission control module, ABS control module, etc., to 'talk' to each other. If there's a break in this communication – say, due to a corroded or damaged connector – data cannot be transmitted correctly. This can cause seemingly unrelated problems, like overheating, because the engine control module isn't getting the correct information from other sensors, or isn't able to properly control the cooling system. Given your symptoms and mileage, a faulty connection is a likely culprit. However, it's difficult to diagnose definitively without proper diagnostic tools. Therefore, I recommend taking your Skoda Roomster to a qualified workshop to have the CAN bus and the control unit connections thoroughly checked. They will be able to read any error codes stored in the system and pinpoint the exact cause of the communication fault.

Thank you for the detailed explanation. As suggested, I took the car to a workshop. It turned out to be a defective plug connection related to the control unit, specifically causing a CAN bus communication fault. They replaced the plug and the associated wiring, which resolved the issue. The total repair cost was 95€.