Because thermal efficiency of electronically controlled diesel engine is higher than that of gasoline engine, heat loss to cylinder wall is lower. This enables electronically controlled diesel engine to generate high power and have high fuel efficiency.

However in other point of view, due to low engine coolant temperature, heating efficiency lowered then, driver is unsatisfied with the heating. To cope with this situation, PTC heater is installed in coolant line and it raises heating efficiency and raise coolant temperature.

ECM activates heater relay 1 and 2 when engine coolant temperature is below 70℃ and engine speed is above 700RPM.

※ Heater relay operation inhibited condition : engine coolant temperature above 70℃, engine speed below 700RPM(to prevent battery discharge)