System Description
This engine uses a water-cooled charge air cooler (CAC).
The CAC charging system has an independent cooling water circuit and circulates coolant from charge air cooler to sub radiator by using electric water pumps.
Electric water pump 2 is not used for turbo low pressure model.
Water Pump and Cooling Fan Control During Engine Running
The charge air cooler (CAC) cooling water pump is controlled by two-stage speeds (High/Low) method.
ECM judges revolution speed of the water pump by calculating engine speeds and engine load and applying this information to the ECM-memorized control MAP.
Furthermore, ECM monitors an estimated ambient temperature calculated based on an intake air temperature sensor signal and a CAC coolant temperature calculated based on a CAC coolant temperature sensor signal.
When the temperature difference between these two becomes wide during the low-speed control of the water pump, the water pump is switched to the high speed control and the cooling fan is activated.
ECM inhibits the operation of the water pump when the following condition is satisfied.
- Source voltage is abnormally high or low.
- CAC coolant temperature is -40 deg.C (-40 deg.F) or less.