What symptoms will occur if the Passat coolant temperature sensor signal is too high?
3 Answers
If the Passat coolant temperature sensor signal is too high, it will cause the temperature gauge needle to stop moving; it may also cause the temperature gauge needle to directly point to the highest position; and it may lead to inaccurate temperature detection. Solutions for an excessively high coolant temperature sensor signal: An excessively high coolant temperature sensor signal indicates that the vehicle's coolant temperature sensor is damaged and needs to be replaced. When replacing the coolant temperature sensor, the vehicle's antifreeze should also be replaced simultaneously, as antifreeze leakage will occur during the sensor removal process. Replacement is the best solution. Function of the coolant temperature sensor: Most cars use water-cooled engines, which rely on continuous coolant circulation to remove excess heat. Water-cooled engines are equipped with coolant temperature sensors to monitor the coolant temperature. The role of the coolant temperature sensor is to convert the coolant temperature into an electrical signal.
My Passat had an issue with the coolant temperature sensor sending excessively high signals a while ago. The most obvious symptom was the dashboard temperature gauge maxing out, with the needle hitting the red zone, even though the actual coolant temperature wasn't that high. The engine warning light kept flashing, and the onboard computer constantly reported abnormal coolant temperature. While driving, the engine felt like it was idling excessively, with particularly weak acceleration accompanied by abnormal vibrations. The most annoying part was the cooling fan running at full speed, continuing to buzz even after turning off the engine, rapidly draining the battery. Idling became extremely unstable, with RPMs jumping erratically at red lights. The AC cooling system completely failed, making driving in hot weather feel like a sauna. Later, upon inspecting the wiring harness, we found that oil contamination in the sensor connector caused intermittent contact.
Attention to all Passat owners: When the coolant temperature sensor signal is abnormally high, the vehicle's control logic will go haywire. The ECU mistakenly assumes the engine is overheating and forcibly activates protection mode. This triggers several issues: The fuel system continuously enriches the mixture, causing fuel consumption to skyrocket—my car burned an extra 2 liters per 100 km; ignition timing gets delayed, resulting in noticeable power loss, especially when climbing hills; the auto start-stop function completely fails, making traffic jams extra fuel-hungry; gear shifts become sluggish, with RPMs revving excessively high during upshifts. These chain reactions also severely damage the catalytic converter—exhaust fumes become unbearably foul. At the first sign of trouble, immediately read the fault codes. Don't repeat my mistake of letting minor issues escalate into major repairs.
