Isuzu Ascender: Electrical System Instruction - page 55

100-3
HEADLIGHTS AND FOG LIGHTS
PPL
0.8
FUSE
BLOCK-
UNDERHOOD
Connector
C4
F6
HOT AT ALL TIMES
FOG LP
Fuse 11
10A
FOG LP
RELAY 39
See Ground
Distribution,
page 14-2.
FUSE
BLOCK-
UNDER-
HOOD
Connector
F3
C1
C5
C4
BLK
0.8
BLK
0.8
B
BLK
0.8
G107
C2
C2
D1
A
FOG
LAMP-
LF
Connector
PPL
0.8
BLK
0.8
B
BLK
1
G103
A
FOG
LAMP-
RF
Connector
See Ground
Distribution,
page 14.
BLK
1
HEADLAMP
SWITCH
Connector
A
Fog
Lamp
Switch
C
Fog Lamp
Indicator
DK GRN/
WHT
0.35
C2
E11
Fog
lamp
relay and
indicator
control
F6
Fog
lamp
switch
C2
C2
DK GRN/WHT
0.35
BODY
CONTROL
MODULE
(BCM)
Connector
ORN
0.35
A
To A on
page 100-1
To B on
page 100-1
See Ground
Distribution,
page 14-2.
Circuit Schematic
100-4
120Ć3
Headlamps
The headlamp driver module (HDM) is an electronic
module that provides electrical power to the vehicle low
beam headlamps. The HDM is controlled by a pulse
width modulated (PWM) ground signal from the body
control module (BCM). The BCM determines the
desired lamp intensity using the ambient light sensor,
multifunction switch and the park brake switch as
inputs. In general, the HDM will operate in 1 of 3 modes:
S
Reduced Intensity Mode: This mode is used by
features that do not require or allow maximum low
beam headlamp intensity such as daytime running
lights (DRL) (nominal: 85% duty cycle).
S
Full Intensity Mode: This mode is used by features
that require full low beam headlamp intensity such
as low beam headlamp operation in manual or auto
modes (nominal: 100% duty cycle).
S
Off Mode: This is the default mode of the system
that will occur when none of the features described
above are active. The BCM will deactivate its PWM
output (0% duty cycle) during this mode.
The normal battery voltage input to the HDM must be
between 6 and 16 volts DC to operate. Any deviation to
these values could cause improper operation.
Major components of this system are the BCM, HDM,
ambient light sensor, multifunction switch, park brake
switch and low beam headlamps.
The headlamps may be turned on in 3 different ways.
First, when the driver places the headlamp switch in the
HEADLAMP
position,
normal
operation
occurs.
Second, with the headlamp switch is placed in the
AUTO position, automatic lamp control (ALC) occurs.
During ALC control, the headlamps will be in daytime
running lamp (DRL) operation in daylight conditions, or
low beam operation in low light conditions. Third, in
wiper activated headlamp (WAH) mode. Only when the
wiper system is activated while the vehicle is in gear,
the wiper blades have completed at least 3 cycles, and
then a 35 second time period expires, will the BCM
switch from DRL mode to headlamp mode during
daylight conditions. When the gearshift lever is placed
in the PARK or NEUTRAL position or if the wipers are
turned off, normal manual or ALC operation will resume
after approximately 60 seconds.
The HDM and high beam relay receive battery positive
voltage directly from the battery. The BCM supplies a
100% duty cycle PWM ground signal to the HDM for
automatic headlight control and normal headlight
operation. The BCM also supplies ground to the high
beam relay coil for high beam headlight operation.
When the driver places the headlamp switch in the
HEADLAMP position and the dimmer switch is in the
low beam position, the HDM switches to full output
sending current flow through the left and right low beam
headlamp fuses to both low beam headlamps. The
dimmer switch sends a ground signal to the BCM in the
high beam position and a momentary ground signal in
the flash-to-Pass (FTP) position from G102 to
deactivate the low beam headlights and activate the
high beam headlights. With the headlights in the low
beam position, the high beams may be momentarily
turned on or flashed by activating the FTP portion of the
switch.
The instrument panel cluster (IPC) illuminates the high
beam indicator when the body control module (BCM)
detects that the high beams are requested. The IPC
receives a class 2 message from the BCM requesting
illumination.
The Headlamps On at Exit and Perimeter Lighting
modes can be adjusted using the steering wheel
controls to select the desired fuction as displayed in the
driver information center. The Headlamps On at Exit
selection will allow the driver to customize the period of
time that the headlamps remain illuminated upon
exiting the vehicle. This period can be adjusted from 0
seconds to 180 seconds. The Perimeter Lighting
feature allows the driver to select if they desire the
headlamps and backup lamps to illuminate when the
door UNLOCK button on the key fob is activated. This
feature can be turned ON or OFF by using the driver
information center steering wheel control buttons.
Circuit Operation
HEADLIGHTS AND FOG LIGHTS
100-5
Daytime Running Lamps (DRL)
The ambient light sensor is a light sensitive transistor
that varies its voltage signal to the body control module
(BCM) in response to changes to the outside (ambient)
light level. When the BCM receives this signal it will
either turn on the daytime running lamps (DRL)
throught the HDM using the reduced output or the
headlamps at full intensity for auto headlamp
operation. Any function or condition that turns on the
headlights will cancel the daytime running lamps
operation. The daytime running lamps (DRL) are the
low beam headlights at a reduced intensity. With the
headlight switch in the OFF position, the headlights will
either be turned ON or OFF, after an approximate 8
second delay depending on whether daylight or low
light conditions are sensed. When the BCM signals the
HDM for DRL operation in daylight conditions, the HDM
illuminates the low beam headlights at a reduced
intensity. The DRL will operate when the ignition switch
is in the RUN position, the gear selector is not in the
PARK position and the parking brake is released. When
these conditions have been met and the ambient light
sensor indicates daytime conditions, the DRL will
illuminate.
On vehicles equipped with the 4-position headlamp
switch, the DRL feature can be temporarily disabled by
momentarily placing the headlamp switch in the DRL
defeat position. This will signal the BCM to disable the
DRL function until the headlamp switch is momentarily
placed in the DRL defeat position again or until the next
ignition key cycle.
DRL operation in Manual Transmission equipped
vehicles will occur when the ignition switch is in the
RUN position, and the parking brake is released.
Fog Lamps
With both the ignition switch in the RUN position and the
park lamps or low beam head lamps on, the fog lights
will illuminate when the driver presses the fog lamp
switch. The FOG LAMP fuse in the engine wiring
harness junction block supplies battery positive voltage
to the fog lamp relay. With the headlamp switch in either
the park or headlamp position and the fog lamp switch
is pressed, the body control module (BCM) will
energize the fog lamp relay control circuit. The current
flow is from the fog lamp relay to both front fog lamps
and to ground G107 and G103. The state of the fog
lamps either ON or OFF will remain the same until the
fog lamp switch is pressed again, or the ignition switch
is cycled OFF and ON. Fog lamp operation will be
cancelled whenever the park lamps are turned OFF or
the high beam headlights have been selected.
Circuit Operation
HEADLIGHTS AND FOG LIGHTS
100-6
HEADLIGHTS AND FOG LIGHTS
(Refer to Section 201 for photographs.)
Component
Photo No.
Ambient Light Sensor
In the center of the upper IP trim panel
89
. . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ambient Light/Sunload
Sensor Assembly
In the center of the I/P upper trim panel
89
. . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Body Control Module
(BCM)
On Rear Fuse Block, under left rear seat
53
. . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fog Lamp-LF
Behind left front bumper
28
. . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fog Lamp-RF
Behind right front bumper
28
. . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Wiper Motor
Under cowl cover (cover removed)
17
. . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse Block-Rear
Under the left rear seat
52
. . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse Block-Underhood
Left side of engine compartment
3
. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
HDLP-HI Relay 43
In the Underhood Fuse Block
50
. . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
HDM Relay 46
In the Underhood Fuse Block
50
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamp Switch
On the left side of the IP
61
. . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamp-Left
Left Front Engine Compartment
2
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamp-Right
Right Front Engine Compartment
2
. . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SP201
Near right front of lower console
80
. . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn Signal/Multifunction
Switch
On the stalk, on the left side of the steering column
71
. . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .
Connector
C201 (17-BLK), (18-BLK),
and (13-GRY)
At base of steering column
120
. . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ground
G101
Left side of engine compartment
4
. . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G102
Left side of engine compartment
4
. . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G103
Right rear of engine compartment
15
. . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G107 (4.2L)
Lower left side of engine
37
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G107 (5.3L)
Lower left side of engine
38
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G108 (4.2L)
Lower left side of engine
37
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G108 (5.3L)
Lower left side of engine
38
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G201
Near right front of lower console
80
. . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Component Location Index
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