2-78 Vehicle Access
Description and Operation
Door Ajar Indicator Description and
Operation
Door Ajar Indicator System
Components
The door ajar indicator system consists of the following
components:
• Body control module (BCM)
• Instrument cluster
• Driver door latch
• Passenger door latch
• Left rear door latch
• Right rear door latch
• Driver window motor
• Passenger window motor
• Left rear side door window switch
• Right rear side door window switch
Driver and Passenger Door Ajar
The window motor supplies a 12 V signal to the door
ajar switch within the door latch, when a door is open
the door ajar switch closes pulling the 12 V signal low.
When the window motor detects the drop in the 12 V
signal circuit, it will then communicate this status to the
BCM via local interconnect network (LIN) bus. The
BCM communicates with the instrument cluster via
serial data message. The instrument cluster, upon
receipt of this serial data message, will illuminate the
door ajar indicator and also send a serial data message
to the radio to activate the door ajar audible warning
when the vehicle speed is greater then 8 km/h (5 mph).
Rear Doors Ajar
The rear side door window switches each provide a
12 V signal to their respective door ajar switch signal
circuits. The rear door ajar switches are integral to each
rear door latch assembly. When a rear door is opened,
the normally open door ajar switch closes. With the
door ajar switch closed, ground is provided to the door
ajar switch signal circuit and the voltage within the
signal circuit drops. The rear side door window
switches will detect the voltage drop and will send a
serial data message to the body control module which
will then send a message to the instrument cluster to
command the door ajar message
Endgate Description and
Operation (QT6)
System Description
The power endgate system consists of the following
components:
• Rear gate module
• Pickup box endgate power assist actuator
• Pickup box endgate position sensor (part of the
power assist actuator)
• Interior pickup box endgate control switch (Part of
the Instrument panel multifunction switch)
• Exterior pickup box endgate control switch
• Right pickup box endgate latch assembly
• Left pickup box endgate latch assembly
• Keyless entry transmitter
• Remote control door lock receiver
Operation
The power endgate can be commanded to power open
and power close by the following methods:
• An open or close command from the interior
pickup box endgate control switch
• An open or close command from the exterior
pickup box endgate control switch
• An open or close request by a signal from the
keyless entry transmitter to the remote control
door lock receiver
The rear gate module will respond to a request by
commanding the left and right pickup box endgate
latches to release the endgate and activate the pickup
box endgate power assist actuator and lower the
endgate or to raise and cinch the endgate closed.
Power Latch
The rear gate module continuously monitors power
endgate operation and calculates its location and
direction of travel from an endgate position sensor (part
of the power assist actuator). One input returns the
position of the endgate relative to the x-axis and y-axis.
The rear gate module then uses these 2 inputs together
to calculate its angle relative to the endgate.
The left and right pickup box endgate latches are
bi-directional motors and latch or unlatch operation is
the result of the direction of the motor rotation. The rear
gate module controls the left and right pickup box
endgate latches through the control circuits by
supplying power and ground in the appropriate polarity.
The motor control circuits are monitored by the rear
gate module prior to activation for a high or low
condition and during motor operation for an insufficient
current flow condition. The ratchet, pawl and sector
switches are part of the left and right pickup box
endgate latches and are used by the rear gate module
to determine the state of the latch during the process of
latching or unlatching . Each of the latch switch signal
circuits are supplied battery voltage and monitored
within the rear gate module. The latch switches share a
common low reference circuit from the rear gate
module and when the switch contacts close the signal
circuit goes low and the rear gate module determines
the switch to be active. The ratchet, pawl and unlatch
switches are inactive when the endgate is closed and
will transition to active as the endgate is opened. The
sector switch will be inactive when the endgate is
closed, during opening of the endgate the sector switch
will change to active and back to inactive when the
endgate is in the fully open position.
The exterior pickup box endgate control switch signal
circuit is supplied battery voltage by the rear gate
module. When the switch is pressed the contacts close
and the signal circuit goes low, the rear gate module
will detect the voltage drop and will command the
endgate to release and lower or to power raise the
endgate to the closed position.
2022 - Silverado 1500 (New) Electrical Body Builder Manual
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