Diagnostic concept for valve controlled coolant bypass paths

摘要

A system and method for determining whether a shut-off valve has failed in a cabin heater bypass line of a thermal subsystem associated with an internal combustion engine that uses electrical power from the pump for a pump that pumps the cooling fluid through the bypass line. The method includes setting a predetermined constant speed of the pump and then providing a valve command that opens the bypass valve. The method then determines whether the pump electrical current has increased or remained substantially the same when the bypass valve is commanded to open and determines that the bypass valve has not opened when the pump electrical current remains substantially constant, when the bypass valve is commanded to open.