LO 11-9 Explain the application of heavy-duty on-board diagnostics and the use of electrical actuators and electronic controls in hybridized diesel engine cooling systems

Heavy-Duty On-Board Diagnostics and Cooling Systems

An OBD system for diesels is required to monitor the cooling system for correct operation so that proper cooling system temperature is reached within a reasonable time. This is an important requirement to enable other OBD monitors and any emissions control strategy dependent upon the cooling system quickly reaching its correct temperature. Data derived from the engine coolant temperature (ECT) sensor will indicate whether the engine has reached near the thermostat’s regulating temperature within a predetermined amount of time. Slow or inadequate engine warm-up will set fault codes.