System Description

COOLING FAN CONTROL

Sensor

Input Signal to ECM

ECM function

Actuator

Crankshaft position sensor (POS)
Camshaft position sensor (PHASE)

Engine speed⁽¹⁾

Cooling fan control

IPDM E/R (Cooling fan relays)

Battery

Battery voltage⁽¹⁾

Wheel sensor

Vehicle speed⁽²⁾

Engine coolant temperature sensor

Engine coolant temperature

Air conditioner switch

Air conditioner ON signal⁽²⁾

Refrigerant pressure sensor

Refrigerant pressure

⁽¹⁾	The ECM determines the start signal status by the signals of engine speed and battery voltage.

⁽²⁾	This signal is sent to ECM via the CAN communication line.

The ECM controls the cooling fan corresponding to the vehicle speed, engine coolant temperature, refrigerant pressure, and air conditioner ON signal. The control system has 3-step control [HIGH/LOW/OFF].

Cooling Fan Operation

Fig 1: Engine Coolant Temperature Vs Vehicle Speed Graph

Courtesy of NISSAN NORTH AMERICA, INC.

Cooling Fan Relay Operation

The ECM controls cooling fan relays in the IPDM E/R via the CAN communication line.

Cooling fan speed	Cooling fan relay
Cooling fan speed	LO	HI
Stop (OFF)	OFF	OFF
Low (LOW)	ON	OFF
High (HI)	ON	ON