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30
ENGINE COOLING FANS
Cooling Fan
Fan Relay 45
Powertrain Control Module (PCM) (4.2L)
Powertrain Control Module (PCM) (5.3L)
Component Index
30-0
ENGINE COOLING FANS
BLK
BLK
1
WHT
0.35
GRY
0.35
POWERTRAIN
CONTROL
MODULE
(PCM)
(4.2L)
(5.3L)
Connector 4.2L
Connector 5.3L
HOT IN RUN AND
START
GRY
0.35
WHT/BLK
0.35
DK BLU
0.35
FUSE
BLOCK-
UNDERHOOD
Connector
FAN
RELAY 45
Cooling
fan speed
signal
5 volt
reference
FAN
Fuse 20
10A
Ground
5 volt
reference
Cooling
fan
speed
signal
Low
reference
COOLING
FAN
Connector
WHT
See
Ground
Distribution,
page 14-6.
Hall
sensor
Cooling
fan
clutch
supply
voltage
C3*
60
C1*
43
C1
60
C100
Connector
C
GRY
0.35
DK BLU
0.35
BLK
0.5
BLK
1
GRY
0.35
GRY
0.35
DK BLU
GRY
GRY
C1*
57
C1**
42
C1**
8
C2**
30
G108
(4.2L)
(5.3L)
G103
BLK
1
*4.2L
**5.3L
C4
a3
C1
e6
C105
Connector
c
b
a
c
d
e
b
a
C2
A5
6
4
5
2
Cooling
fan clutch
control
Low
reference
C107**
Connector
A2
B10
DK BLU
0.35
GRY
0.35
C118
Connector
B
A
E
D
C
See
Ground
Distribution,
page 14-3.
See Ground
Distribution,
page 14-3.
BLK
3
Circuit Schematic
30-1
ENGINE COOLING FANS
120Ć3
Cooling Fan Control
The purpose of the electro-viscous (EV) fan clutch is to
maintain
powertrain
cooling
requirements.
The
powertrain
control
module
(PCM)
monitors
the
following sensors to regulate the fan speed;
S
Engine coolant temperature sensor
S
A/C refrigerant pressure sensor
S
Vehicle speed sensor
S
Intake air temperature sensor
S
Transmission fluid temperature sensor
S
Ambient air temperature sensor
The PCM controls the electro-viscous fan clutch
engagement. The PCM regulates a 12-volt pulse width
modulated signal (PWM) to the cooling fan relay. The
PWM signal determines the ON time of the relay. As the
commanded state of the fan clutch increases, so does
the ON time of the relay. This ON time directly effects
the amount of time the solenoid, which is internal to the
fan clutch, is energized. When the solenoid in the fan
clutch is energized, it opens the spring loaded valve
and allows fluid to flow from the storage chamber to the
fluid coupling of the cooling fan clutch, increasing the
fan speed. When the solenoid is de-energized, the
spring loaded valve closes, and blocks the path of the
fluid to the fluid coupling of the fan clutch, reducing fan
speed.
The fan has the ability to create a feedback signal, so
the PCM has an actual fan speed input. This is done
with a hall effect sensor internal to the fan clutch. The
PCM supplies a 5-volt reference and a low reference to
the hall effect sensor. The hall effect sensor returns a
signal pulse through the cooling fan speed signal circuit
in response to the reluctor track passing by the
magnetic field of the hall effect sensor.
The PCM commands the cooling fan to 100% under the
following conditions:
S
Engine coolant temperature exceeds
approximately 129
_
C (264
_
F).
S
The transmission oil temperature exceeds
approximately 151
_
C (304
_
F).
S
A/C refrigerant pressure exceeds 1655 kPa
(240 psi).
S
When certain DTC’s set. These include P0116,
P0117, P0118, P0125, P1481, P1482, and P1484.
The scan tool can engage the cooling fan clutch. This is
done with the engine controls special function menu
screen. To engage the cooling fan, It can take up to 2
minutes for a 100% command with the engine at 2000
RPM. The lower the engine speed, the longer it will take
the fan to engage. To disengage the cooling fan, it can
take up to 2 minutes with the engine at 2000 RPM. The
lower the engine speed, the longer it will take to
disengage. In lower ambient air temperatures the
cooling fan will engage in less time, however, it will take
longer to disengage due to the properties of the fluid vs.
temperature.
Under certain conditions the cooling fan may be
engaged at engine restart. They are as follows;
S
The cooling fan was engaged at the time the engine
was turned off
S
The fluid may bleed from the storage chamber into
the fluid coupling of the cooling fan
Although the fan is commanded off at this time due to a
cold start condition. This is the most likely time a vehicle
driver will notice that the fan noise is excessive
compared to normal engine starts with out cooling fan
engaged. As the engine speed is increased the fan
noise will be louder than before. These are normal
conditions that can be very intermittent.
Circuit Operation
30-2
ENGINE COOLING FANS
(Refer to Section 201 for photographs.)
Component
Photo No.
Cooling Fan
Top left side of radiator fan shroud
2
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Relay 45
In the Underhood Fuse Block
51
. . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Powertrain Control Module
(PCM) (4.2L)
Left front of engine
5
. . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Powertrain Control Module
(PCM) (5.3L)
Left front of engine compartment
25
. . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connector
C100 (4.2L) (10-BLK)
Left front of engine
5
. . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C105 (10-BLK)
Left side of engine compartment
4
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C107 (5.3L) (38-BLK)
Left rear of engine compartment
18
. . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C118 (6-BLK)
Top left side of radiator fan shroud
2
. . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ground
G103
Right rear of engine compartment
15
. . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G108 (4.2L)
Lower left side of engine
37
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G108 (5.3L)
Lower left side of engine
38
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Component Location Index
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