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15-8
(3) Components for ECU Output
CAN
E-EGR cooler
bypass valve
- Instrument cluster
- TCU
- Self diagnosis
PTC heaterCooling fan
E-EGR valve
Variable swirl valveE-VGT actuatorIMV valve
A/C compressorInjectorThrottle position
sensor
- Glow plug unit
- ABS & ESP unit
- GCU
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15-370000-00
HFM (intake air
temperature)Cooling fan module
DSI 6 A/T (ATF
temperature)Coolant
temperature senso
r
Refrigerant
pressure sensor
Relay box
(12) Cooling fan control
A. Overview of cooling fan and A/C compressor
The cooling system maintains the engine temperature at an efficient level during all engine
operating conditions. The water pump draws the coolant from the radiator. The coolant then
circulates through water jackets in the engine block, the intake manifold, and the cylinder head.
When the coolant reaches the operating temperature of the thermostat, the thermostat opens.
The coolant then goes back to the radiator where it cools. The heat from automatic transmission
is also cooled down through the radiator by circulating the oil through the oil pump. ECU controls
the electric cooling fans with three cooling fan relays to improve the engine torque and air
conditioning performance.
For detailed information, refer to Chapter "Air Conditioning System".
B. Components
A/C compressor
D20DTR ECU
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15-38
C. Input/Output for cooling fan and A/C compressor
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15-390000-00
D. Cooling fan and A/C compressor control
Conditions for cooling fan ▶
The cooling fan module controls the cooling fan relay, high speed relay and low speed relay. The
cooling fan is controlled by the series and parallel circuits.
A/C switch Cooling fanCoolant temperature Refrigerant pressure
A/C compressor
OFF OFF Coolant temp. < 90℃ -
LO 90℃ ≤ Coolant temp.
< 105℃-
HI 105℃ ≤ Coolant temp. -
ONLO
Coolant temp. < 105℃Refrigerant pressure <
18 bar
ON
HI 18 bar ≤ Refrigerant
pressure
HI 105℃ ≤ Coolant tem
p.
< 115℃-
HI115℃ ≤ Coolant temp. -
OFF (cut)
A/C compressor OFF conditions ▶
Coolant temperature: below -20℃ or over
115℃
Approx. 4 seconds after starting the engine
Engine rpm: below 650 rpm or over 4500 rpm
When abrupt acceleration
Refrigerant pressure:
* OFF below 2.0 kg/㎠, then ON over 2.4 kg/㎠
* OFF over 30 kg/㎠, then ON below 21.4 kg/㎠ -
-
-
-
-
The output voltage from refrigerant pressure sensor is 1.7 V to 3.5 V when the refrigerant pressure
is 10 to 24 kgf/㎠ with A/C "ON".Output voltage according to refrigerant pressure ▶
Cooling fan controls according to ATF ▶
ATF temperature Fan condition Remark
Over 110˚CHigh speed -
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01-8
Front View ▶
NO. FUNCTION NO. FUNCTION
1 HFM Sensor 12 Intake Manifold
2 Intake Air Duct 13 Cylinder Head
3 Cylinder Head Cover 14 Exhaust Manifold
4 Ignition Coi 15 Dipstick Guide Tube and Gauge
5 Spark Plug Connector 16 Connecting Rod
6 Fuel Distributor 17 Crankshaft
7 Injector 18 Engine Mounting Bracket
8 Exhaust Camshaft 19 Starter
9 Intake Camshaft 20 Crankcase
10 Valve Tappet 21 Oil Pump Sprocket
11 Intake Valve 22 Oil Pan
NO. FUNCTION NO. FUNCTION
23 Camshaft Adjuster 29 Oil Pump Drive Chain
24 Oil Filler Cap 30 Oil Strainer
25 Engine Hanger Bracket 31 Oil Pump
26 Cooling Fan and Viscous Clutch 32 Ring Gear and Flywheel of Drive Plate
27 Oil Filter 33 Piston
28 Timing Chain
Side View ▶
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04-6
2. DESCRIPTION AND OPERATION
1) General Description
The cooling system maintains the engine temperature at an efficient level during all engine
operating conditions.
When the engine is cold, the cooling system cools the engine slowly or not at all. This slow
cooling of the engine allows the engine to warm up quickly.
The cooling system includes a radiator and recovery subsystem, cooling fans, a thermostat and
housing, a water pump, and a water pump drive belt. The timing belt drives the water pump.
All components must function properly for the cooling system to operation. The water pump
draws the coolant from the radiator. The coolant then circulates through water jackets in the
engine block, the intake manifold, and the cylinder head. When the coolant reaches the operating
temperature of the thermostat, the thermostat opens. The coolant then goes back to the radiator
where it cools.
This system directs some coolant through the hoses to the heat core. This provides for heating
and defrosting.
The coolant reservoir is connected to the radiator to recover the coolant displaced by expansion
from the high temperatures. The coolant reservoir maintains the correct coolant level.
The cooling system for this vehicle has no radiator cap or filler neck. The coolant is added to the
cooling system through the coolant reservoir.
2) Radiator
This vehicle has a lightweight tube-and-fin aluminum radiator. Plastic tanks are mounted on the
upper and the lower sides of the radiator core.
On vehicles equipped with automatic transaxles, the transaxle fluid cooler lines run through the
radiator tank.
A radiator drain plug is on this radiator.
To drain the cooling system, open the drain plug.
3) Coolant Reservoir
The coolant reservoir is a transparent plastic reservoir, similar to the windshield washer reservoir.
The coolant reservoir is connected to the radiator by a hose and to the engine cooling system by
another hose.
As the vehicle is driven, the engine coolant heats and expands. The portion of the engine coolant
displaced by this expansion flows from the radiator and the engine into the coolant reservoir. The
air trapped in the radiator and the engine is degassed into the coolant reservoir.
When the engine stops, the engine coolant cools and contracts. The displaced engine coolant is
then drawn back into the radiator and the engine. This keeps the radiator filled with the coolant to
the desired level at all times and increases the cooling efficiency.
Maintain the coolant level between the MIN and MAX marks on the coolant reservoir when the
system is cold.
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04-72112-01
4) Water Pump
The belt-driven centrifugal water pump consists of an impeller, a drive shaft, and a belt pulley.
The impeller is supported by a completely sealed bearing.
The water pump is serviced as an assembly and, therefore, cannot be disassembled.
5) Thermostat
A wax pellet-type thermostat controls the flow of the engine coolant through the engine cooling
system. The thermostat is mounted in the thermostat housing to the front of the cylinder head.
The thermostat stops the flow of the engine coolant from the engine to the radiator to provide
faster warm-up, and to regulate the coolant temperature. The thermostat remains closed while the
engine coolant is cold, preventing circulation of the engine coolant through the radiator. At this
point, the engine coolant is allowed to circulate only throughout the heater core to warm it quickly
and evenly.
As the engine warms, the thermostat opens. This allows the engine coolant to flow through the
radiator wherethe heat is dissipated. This opening and closing of the thermostat permits enough
engine coolant to enter the radiator to keep the engine within proper engine temperature operating
limits.
The wax pellet in the thermostat is hermetically sealed in a metal case. The wax element of the
thermostat expands when it is heated and contracts when it is cooled.
As the vehicle is driven and the engine warms, the engine coolant temperature increases. When
the engine coolant reaches a specified temperature, the wax pellet element in the thermostat
expands and exerts pressure against the metal case, forcing the valve open. This allows the
engine coolant to flow through the engine cooling system and cool the engine.
As the wax pellet cools, the contraction allows a spring to close the valve.
The thermostat begins to open at 82°C(180 °F) and is fully open at 95°C(203°F). The thermostat
closes at 80°C (176°F).
6) Electric Cooling Fan
Keep hands, tools, and clothing away from the engine cooling fans to help prevent personal
injury.
This fan is electric and can turn on even when the engine is not running. -
If a fan blade is bent or damaged in any way, no attempt should be made to repair or reuse
the damaged part. A bent or damaged fan assembly should always be replaced with a new
one to prevent possible injury. -
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04-8
The cooling fans are mounted behind the radiator in the engine compartment. The electric cooling
fans increase the flow of air across the radiator fins and across the condenser on air conditioned
(A/C)-equipped vehicles.
This helps to speed cooling when the vehicle is at idle or moving at low speeds.
All models have two fans. The main fan is 320 mm (12. 6 inches) in diameter with seven blades to
aid the airflow through the radiator and the condenser. An electric motor attached to the radiator
support drives the fan.
The auxiliary fan is 320 mm (12.6 inches) in diameter.
A/C Off or Non-AC Model ▶
The cooling fans are actuated by the engine control module (ECM) using a low-speed
cooling fan relay, a high-speed cooling fan relay and a cooling fan motor relay.
The ECM will turn the cooling fans on at low speed when the coolant temperature reaches
95°C(203°F) and at high speed when the coolant temperature reaches 105°C(221°F).
The ECM will change the cooling fans from high peed to low speed at 100°C(212°F) and
will turn the cooling fans off at 90°C (194°F). -
-
-
A/C On ▶
The ECM will turn the cooling fans on at low speed when the A/C system is on. The ECM
will change to high speed when the high side A/C pressure reaches 1860 kPa (269.8 psi).
The cooling fans will return to low speed when the high side A/C pressure reaches 1378
kPa (199.8 psi). -
-
7) Engine Coolant Temperature Sensor
The Engine Coolant Temperature (ECT) sensor uses a temperature to control the signal voltage to
the Engine Control Module (ECM).
8) Coolant Temperature Gauge
The coolant temperature gauge controls the instrument panel temperature indicator. The coolant
temperature gauge is located with ECT sensor.