Lighting 2-39
when the ignition switch is placed in either the CRANK
or RUN position and then placed in the OFF position,
the BCM initiates a 10 minute timer. At the end of the
10 minutes, the BCM will turn off the control power
output to the park lamp controls as well as the
headlamp relay coils, deactivating the exterior lamps.
This feature will be cancelled if any power mode other
than OFF becomes active. The BCM will disable battery
run down protection if any of the following conditions
exist. The park or headlamp switch is placed in the ON
to OFF position, and back to the ON position during
battery run down protection. The BCM determined that
the park or headlamp switch was not active when the
ignition was turned OFF.
Interior Lighting Systems
Description and Operation
Interior Lamps
The interior lighting system consist of two groups. This
first group includes lamps that may not be dimmed.
• Dome lamps
• Center console compartment lamps
• Reading lamps
• Sunshade mirror lamps
Dome Lamps
The dome lamp switch has 3 positions: DOOR, OFF,
and ON. The ON position provides a ground for
continuous operation and the dome lamp will remain
illuminated until the switch is placed in either the DOOR
or OFF position. When in the DOOR position, the dome
lamp operation is controlled by the body control module
(BCM). When any door is opened, the door ajar switch
contacts close and the BCM receives a door-open
input. The BCM illuminates the dome lamp when any
door is opened or a door lock/unlock request is
activated with the key fob. After all doors have been
closed, the dome lamp will remain illuminated
approximately 3 seconds after the last door closes.
When the driver places the dome lamp switch in the
OFF position, the dome lamp will be disabled. In the
event that the dome lamp were to remain illuminated for
more than 10 minutes with the ignition switch in the
OFF position and no doors opened, the BCM will
deactivate the dome lamp control circuit to prevent total
battery discharge. The dome lamps will turn OFF using
the theater dimming feature when controlled by
the BCM.
Center Console Compartment Lamp
The inadvertent power supply voltage circuit from the
BCM provides battery voltage to the center console
compartment lamp. When the center console is
opened, the center console compartment lamp switch
contacts close providing a path to ground and the
center console compartment lamp illuminates. If the
operator inadvertently leaves the center console
compartment door open with the center console
compartment lamp ON, the BCM will turn all interior
lamps OFF after 10 minutes has passed since any
switch activation has been detected by the BCM.
Reading Lamps
The inadvertent power supply voltage circuit from the
BCM provides battery positive voltage to each reading
lamp. When a reading lamp switch is activated, the
switch contacts close providing a path to ground and
the reading lamp illuminates. If the operator
inadvertently leaves a reading lamp ON, the BCM will
turn all interior lamps OFF after 10 minutes has passed
since any switch activation has been detected by
the BCM.
Sunshade Mirror Lamps
The inadvertent power supply voltage circuit from the
BCM provides battery voltage to each set of sunshade
mirror lamps. When the sunshade mirror cover is
opened, a switch closes providing ground and the
sunshade lamps illuminate. If the operator inadvertently
leaves a sunshade mirror cover open with the lamps
ON, the BCM will turn all interior lamps OFF after
10 minutes has passed since any switch activation has
been detected by the BCM.
Keyless Entry Interior Illumination
When the operator uses the keyless entry transmitter in
order to unlock the doors, the BCM receives a
door-unlock signal. The BCM must receive inputs from
various systems that indicate that the ignition switch is
OFF, the courtesy lamp switch is OFF, and all doors are
closed before the BCM will activate the interior lamps.
After all doors have been closed, the courtesy lamps
will turn OFF immediately if the ignition switch is turned
to the ON position, the door locks are LOCKED,
or approximately 20 seconds after the last door closes.
The BCM will turn off the courtesy lamps through the
theater dimming feature. The BCM keeps the courtesy
lamps on for 40 seconds after an alarm event is
completed.
Interior Lamps Dimming
The second group includes lamps which may be
dimmed. This group may use a combination of light
emitting diodes (LED), incandescent lamps, and pulse
width modulation (PWM) illumination.
• Dome/reading lamps – front
• Dome/reading lamps – rear
• Door lock switch – driver
• Door lock switch – passenger
• Headlamp switch
• HVAC control head assembly
• Multifunction switch – instrument panel
• Outside rearview mirror switch
• Park brake switch
• Radio
• Roof beacon switch
• Seat memory switch – driver
• Steering wheel control switch – left
• Steering wheel control switch – right
• Sun roof switch
• Sun roof tilt switch
• Transfer case shift control switch
• Trailer brake control switch
2021 - Silverado 4500HD, 5500HD, and 6500HD Electrical Body Builder Manual
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