What code P0425 means and how to rectify the problem?

Code P0425 indicates a problem with the coolant temperature sensor circuit, specifically the sensor's performance or signal. To rectify this issue, first, inspect the wiring and connectors for damage or corrosion, then test the coolant temperature sensor for proper operation using a multimeter. If the sensor is faulty, replace it. Additionally, check the engine's coolant level and ensure there are no overheating issues, as these can also impact sensor performance.