Wiring Systems and Power Management 7-437
Retained Accessory Power
Description and Operation
3282830
The body control module (BCM) monitors the ignition
switch position, battery condition, and each door ajar/
open switch status to determine whether the retained
accessory power should be initiated or terminated.
Retained accessory power is controlled by two different
methods; relay control and serial data. Some modules
receive a retained accessory power message from the
BCM over the serial data circuits. Serial data controlled
retained accessory power is deactivate d as required by
their modules retained accessory power mode
operation. Other subsystems are activated directly by
the BCM through a relay. Components and systems
that are active in retained accessory power are also
activated anytime the ignition is any position other than
OFF regardless of the door switch signals.
Relay Controlled Retained Accessory
Power
The BCM keeps the retained accessory power relay 1
and retained accessory power relay 2 energized during
all power modes, except Off-Awake and Crank. The
retained accessory power relay 1 and retained
accessory power relay 2 are also energized for
approximately 10 minutes after shutting the ignition
OFF and removing the key, providing no door is
opened.
Relay controlled retained accessory power will end
when one of the following conditions is met:
• The BCM receives an input from any door ajar or
open switch indicating the opening of any door
after the ignition key is out of the ignition.
Note: If the BCM is receiving any door ajar or
open signal from those switches when the ignition
key is turned OFF, retained accessory power will
not initiate.
• The BCM internal timer for the retained accessory
power expires after approximately 10 minutes.
• The BCM detects a decrease in battery capacity
below a prescribed limit.
Systems powered by the retained accessory power
relay 1 and retained accessory power relay 2 during the
retained accessory power mode are as follows:
Note: The vehicle may not be equipped with all
components as listed below.
• Accessory Power Receptac le
• Cigarette Lighter Receptacle
• Sunroof Control Module
• Sunroof Switch
• Sliding Rear Window Switch
• Mobile Device Wireless Charger Module
2021 - Silverado 4500HD, 5500HD, and 6500HD Electrical Body Builder Manual
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