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15-38
Relay box
A/C
compressorHFM (intake air
temperature)Cooling fan
module
MB 5 A/T (ATF
temperature)Coolant
temperature
sensor
(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
D20DTR ECU
Refrigerant
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15-40
D. Cooling fan and A/C compressor control
Conditions for cooling fan control ▶
The PWM cooling fan is set by coolant temperature and A/C refrigerant pressure. And, the setting
value in A/T equipped vehicle may vary according to the internal oil temperature. The The engine ECU
controls the PWM cooling fan unit based on various signals to get the optimized temperature during
engine running.
PWM cooling fan control according to coolant temperature and vehicle speed -
The PWM cooling fan starts running
from 89℃ of coolant temperature
PWM cooling fan control according to transmission fluid temperature (A/T)
1. PWM duty under 129℃: 0%
2. PWM duty over 130℃: 94.4% -
PWM cooling fan control according to A/C refrigerant pressure -
PWM duty value sharply increases
when the A/C refrigerant pressure
goes over 10 bar. And, it slowly
decreases when A/C refrigerant
pressure goes down below 14 bar
(A/C compressor OFF). PWM duty
Refrigerant
pressure (bar)under 101℃: The PWM dut
y value
decreases when the vehicle speed
increases
over 105℃: The PWM duty value
is fixed at 94.4% -
-
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15-410000-00
A/C compressor OFF conditions ▶
Coolant tem
perature: below -20℃ or over
115℃
Engine rpm: over 4500 rpm
Engine rpm: below 600 rpm
When abrupt acceleration
Very high load during idling
Refrigerant pressure: over 32 bar or below 2
bar
Failure in refrigerant sensor, coolant
temperature sensor, and cooling fan -
-
-
-
-
-
-
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15-42
PTC Fuse and Relay
(13) PTC heater control
A. Overview
The supplementary electrical heater is installed in DI engine equipped vehicle as a basic equipment.
The PTC system is operated according to two temperature values measured at the coolant temperature
sensor and HFM sensor. This device is mounted in the heater air outlet and increase the temperature of
air to the passenger compartment. Because PTC system is heated by electrical power, high capacity
alternator is required. PTC does not operate during engine cranking, while the battery voltage is lower
than 11 V or during preheating process of glow plugs.
B. Components
HFM (intake air
temperature)
Coolant temperature
sensor
PTC relay 1
D20DTR ECU
PTC relay 2
PTC fuse 1, 2, 3, 40A
PTC heater
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15-430000-00
C. PTC operation process
The PTC operating condition (ON) is controlled in two steps.
Basically, the engine ECU controls the relay to supply the power to PTC according to the coolant
temperature sensor and ambient temperature sensor.
1st step (initial operation of PTC) ▶
Coolant temperature < 15°C: PTC ON
Coolant temperature ≥ 15°C: PTC ON after satisfying the conditions in 2nd step -
-
2nd step (coolant temperature ≥ 15°C) ▶
Coolant temperature ≤ 65°C and intake air temperature ≤ -10°C: PTC ON
Coolant temperature < 60~65°C and intake air temperature < -10~0°C: PTC ON
Coolant temperature ≤ 60°C and intake air temperature ≤ 0~5°C: PTC ON -
-
-
Stop (OFF) conditions ▶
A/C blower switch OFF
Defective ambient air temperature sensor (including open or short circuit)
Engine cranking
Low battery voltage (below 11V)
During pre-glow process (glow indicator ON) -
-
-
-
-
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07-6
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 slo
w
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.
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08-6
3. IGNITION SYSTEM OPERATION
This ignition system does not use a conventional distributor and coil. It uses a crankshaft position
sensor input to the Engine Control Module (ECM).
The ECM then determines Electronic Spark Timing (EST) and triggers the electronic ignition system
ignition coil.
This type of distributor less ignition system uses a "waste spark" method of spark distribution. Each
cylinder is paired with the cylinder that is opposite it (2.3L DOHC: 2 - 3 or 1 - 4, 3.2L DOHC: 1 - 6 or 2 -
5 or 3 - 4).
The spark occurs simultaneously in the cylinder coming up on the compression stroke and in the
cylinder coming up on the exhaust stroke.
The cylinder on the exhaust stroke requires very little of the available energy to fire the spark plug.
The remaining energy is available to the spark plug in the cylinder on the compression stroke. These
systems use the EST signal from the ECM to control the EST.
The ECM uses the following information: Engine load (mass air flow sensor, manifold air pressure
sensor).
Engine coolant temperature.
Intake air temperature.
Crankshaft position.
Engine speed (rpm).
1) Electronic Ignition System Ignition Coil
The Electronic Ignition (EI) system ignition coil is located on the cylinder head cover.
The double ended coils receive the signal for the ECM which controls the spark advance. Each
EI system ignition coil provides the high voltage to two spark plugs simultaneously;
3.2L DOHC
T1/1: cylinder 2 and 5
T1/2: cylinder 3 and 4
T1/3: cylinder 1 and 6
The EI system ignition coil is not serviceable and must be replaced as an assembly.
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01-156810-30
3. SYSTEM BLOCK DIAGRAM
A/C compressor OFF conditions ▶
Coolant temperature: over 115℃
Engine speed: over 4,500 rpm for more than 2 seconds
Engine speed: below 650 rpm
Maximum output due to abrupt acceleration
Excessive acceleration
Increased load during engine idling (to prevent the engine from shutting off)
Refrigerant pressure: over 32 bar or below 2 bar
Defects in A/C related system (refrigerant pressure sensor, coolant temperature sensor, cooling fan) 1.
2.
3.
4.
5.
6.
7.
8.