Golf 5 2.0L Comfortline (2005) - P0116-008 ECT Sensor Fault & Radiator Fan Issue
I own a 2005 Volkswagen Golf 5 2.0L Comfortline. Recently, the radiator fans have been turning on automatically when starting the car and remain active for about one to two minutes after engine shutdown. I took it to a Bosch repair center, where they identified a faulty Engine Coolant Temperature (ECT) sensor (G62) as the cause. After replacing the sensor and clearing the error code, the issue temporarily resolved but returned after some time. Upon further investigation, I found that the following diagnostic trouble code appears when the fans stay on: "1650- Engine Coolant Temp Sensor (G62) - Implausible Signal - P0116-008". The problem disappears once the code is cleared. However, it only reoccurs after longer driving trips—typically around 25 km. I usually make short trips of about 4 to 5 km to and from work. During these, the temperature gauge reads around 90°C, and the fans do not activate. Only during extended drives (e.g., 25 km) do the fans turn on—both at cold start and hot start—and remain active while driving, staying on for up to two minutes after engine shutdown. After clearing the code, the issue only surfaces following long-distance travel. This suggests a possible correlation between driving duration and sensor behavior. I'm seeking advice on how to properly diagnose or resolve this recurring ECT sensor (G62) issue with P0116-008 in my Golf 5 2.0L model, especially given the intermittent nature of the problem and its link to trip length.
Check the official trouble code explanations for P0116-008 on trusted automotive diagnostic resources. If your coolant level is adequate, it's possible the repair center overlooked the real root cause or installed a defective ECT sensor. If you're doing a DIY fix, begin by comparing the Intake Air Temperature (IAT) to the ECT when the engine is cold—these should be within a few degrees of each other. Next, verify that the ECT reading matches the thermostat's opening and closing temperature ratings, and note at what temperature the cooling fans activate. Perform these checks at idle with AC or defrost off to ensure the ECT is solely controlling fan operation. If all these tests pass, consider intermittent wiring issues. You can test this by monitoring scanner readings and manually moving the sensor connections to see if signal fluctuations occur. For a more accurate diagnosis, refer to the official cooling system electrical wiring diagram to understand how the fan control circuit operates.