2-42 Lighting
Turn Signal Lamps
Turn Signals
The K9 Body Control Module (BCM) provides the
S78 Turn Signal Switch with left and right turn signal
switch signal circuits. Ground is applied at all times to
the turn signal/multif unction switch. The turn signal
lamps may only be activated with the ignition switch in
the ON or START positions. When the turn signal/
multifunction switch is placed in either the turn right or
turn left position, ground is applied to the BCM through
either the right turn or left turn signal switch signal
circuit. The BCM responds to the turn signal switch
input by sending a serial data message to the
K219 Lighting Control Module. The Lighting Control
Module responds by applying a pulsating voltage to the
turn signal lamps through there respective control
circuits. When a turn signal request is received by the
BCM, a serial data message is also sent to the
instrument cluster requesting the respective turn signal
indicator be pulsed ON and OFF.
Turn Signal Outage Detection
Vehicles with LED turn signals require additional turn
signal outage detection circuits that provide turn signal
feedback to the K219 Lighting Control Module. The
Lighting Control Module uses the feedback information
to send a serial data message to the instrument cluster
to alert the driver anytime a turn signal fault is detected.
If a fault is detected on a turn signal circuit or a turn
signal feedback circuit, the turn signals will flash in a
rapid manner to alert the driver of the fault.
Backup Lamps
With the engine running and the transmission in the
reverse position, the transmission control module
(TCM) sends a serial data message to the multiple
control modules. The message indicates that the gear
selector is in the reverse position. The K9 Body Control
Module (BCM) responds to the reverse position
message by sending a serial data message to the
K219 Lighting Control Module to request the backup
lamps on. The Lighting Control Module responds by
applying battery voltage to the backup lamps control
circuit(s) illuminating the backup lamps. The applied
voltage is also sent to the A11 Radio and A10 Inside
Rearview Mirror for rearview camera purposes. Once
the driver moves the gear selector out of the reverse
position, a serial data message is sent by the TCM that
the transmission is no longer in the reverse position.
The BCM responds to the reverse position message by
sending a serial data message to the Lighting Control
Module to request the backup lamps off. The Lighting
Control Module responds by removing battery voltage
from the backup lamp circuits. The engine must be
running for the backup lamps to operate.
Cargo Lamps
Cargo Lamps
When the K9 Body Control Module (BCM) receives a
task lamp switch input from the S30 Headlaamp Switch,
the BCM respond s by sending a serial data message to
the K219 Lighting Control Module. The lighting control
module responds by applying pulse width modulated
(PWM) voltage to the cargo lamp control circuits
illuminating the cargo lamps. In the event that the cargo
lamps were to remain illuminated for more than
10 minutes with the ignition switch in the OFF position,
the lighting control module will deactivate the cargo
lamp control circuits to prevent total battery discharge.
Task Lamps
When the K9 Body Control Module (BCM) receives a
task lamp switch input from the S30 Headlaamp Switch,
the BCM respond s by sending a serial data message to
the K219 Lighting Control Module. The lighting control
module responds by applying pulse width modulated
(PWM) voltage to the task lamp control circuits
illuminating the task lamps in each outside rearview
mirror assembly. When the task lamp switch is pressed
a second time, the left task lamp control circuit will stay
illuminated while the right side will be turned off. When
the task lamp switch is pressed a third time, the left task
lamp control circuit will be turned off while the right side
will be turned back on. When the task lamp switch is
pressed a fourth time, both task lamps will be turned
off. In the event that the task lamps were to remain
illuminated for more than 10 minutes with the ignition
switch in the OFF position, the lighting control module
will deactivate the cargo lamp control circuit to prevent
total battery discharge.
Approach Lighting
Approach lighting is commanded ON when the unlock
button is pressed on the keyless entry transmitter
during dark ambient light conditions. When the keyless
entry transmitter unlock button is pressed, a serial data
message is sent by the K9 Body Control Module (BCM)
that the vehicle is being unlocked. The K219 Lighting
Control Module responds to the serial data message by
applying voltage to the approach lamp control circuit
illuminating the LED lighting located under each outside
rearview mirror as part of approach lighting.
Battery Run Down Protection/
Inadvertent Power
To provide battery run down protection, the exterior
lamps will be deactiva ted automatically under certain
conditions. The K9 Body Control Module (BCM)
monitors the state of the S30 Headlamp Switch. If the
headlamp switch is in the park or headlamp position
when the ignition switch is ON and then the ignition
switch is placed in the OFF position, the BCM initiates a
10 minutes timer. At the end of the 10 minutes, the BCM
will send a serial data message to the K219 Lighting
Control Module to deactivate the exterior lamps to
prevent total battery discharge. 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 changed from 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.
2022 - Silverado 1500 (New) Electrical Body Builder Manual
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