Abstract: A first microprocessor controls an actuator according to a control program stored in a program storage memory, using a learnt value stored in a learning value storage memory. The learnt value is updated in response to an action of the actuator. A second microprocessor is connected to the first microprocessor to replace the control program with another control program which also has a function to initialize the learnt value. However, when the learnt value has been updated, the first microprocessor prohibits the second microprocessor from replacing the control program, thereby preventing the impairment of control response due to initialization of the learnt value.

Abstract: A vehicle engine temperature is detected, and a radiator fan fault warning is given so as to prevent engine overheating when this temperature rises to or above a preset determining value under a predetermined test conditions. Preferably, it is determined that the radiator fan has a fault when a temperature equal to or above this determining value holds for at least a predetermined time. More preferably, this determining value is set low while the vehicle is in motion. By providing these supplementary conditions, incorrect diagnosis of a fault in the radiator fan is prevented.