8-14
Shift Lock Control
Description and Operation
Automatic Transmission Shift Lock
Control Description and Operation
The Automatic Transmission Shift Lock Control System
is a safety device that prevents an inadvertent shift out
of PARK when the engine is running. The driver must
press the brake pedal before moving the shift lever out
of the PARK position. The system consists of the
following components:
•
The Automatic Transmission Shift Lock Solenoid
(serviced as the Automatic Transmission Shift
Lock Actuator)
•
The Body Control Module (BCM)
•
The Engine Control Module (ECM)
The BCM controls the voltage to the shift lock control
solenoid though the shift lock control solenoid
controlled voltage circuit. The following conditions must
be met before the BCM will supply voltage to the shift
lock control solenoid:
•
The ignition is in the ON position.
•
The ECM sends an input via GMLAN serial data to
the BCM when the Transmission Control Module
(TCM) indicates the transmission is in the PARK
position.
•
The BCM receives a brake applied input from the
stop lamp switch.
Since the shift lock control solenoid is permanently
grounded, the BCM supplies voltage to the automatic
transmission shift lock control solenoid, releasing the
mechanical lock on the shift lever as the solenoid
energizes. The energized solenoid allows the driver to
move the shift lever out of the PARK position. When the
brake pedal is not applied, the BCM turns the control
voltage output of the shift lock control solenoid OFF,
de-energizing the shift lock control solenoid. When the
transmission is in the PARK position, the de-energized
shift lock control solenoid will prevent shifting as the
lever is mechanically locked in the PARK position.
During remote start operation the BCM will de-energize
the automatic transmission shift lock control circuit,
locking the shift lever in the PARK position
2021 - Silverado 4500HD, 5500HD, and 6500HD Electrical Body Builder Manual
