Description And Operation; Power Take-Off (Pto) Description And Operation - Chevrolet Silverado 4500HD Manual

8-6 Power Take-Off

Description and Operation

Power Take-Off (PTO) Description
and Operation
The power take-off (PTO) is an upfitter integrated
system that allows the user to create an auxiliary power
source. The PTO system specifically controls engine
speed to values higher than normal base idle, PTO load
relay engagement, and remote starting and shutdown
of the engine. When the operator requests PTO, the
PTO switch will be turned ON and the engine RPM will
go to a default standby speed.
The PTO system utilizes the following:
The transmission driven PTO gear
The in-cab PTO switch and cruise control SET
and RES + switches
The PTO telltale indicator
The power take off module (PTOM)
The remote PTO upfitter connector
Note: For specific information on how to set up and
operate the Power Take Off system refer to the vehicle
Duramax Diesel supplement manual and the GM
Upfitter website.
Factory Installed PTO Components
The in-cab PTO switch and cruise control SET
RES + switches
The PTO switch is a part of the switch bank and is
mounted in the right side of the center instrument
panel. The PTO switch is a two position momentary
switch with two states: ON/OFF. When the PTO switch
is pressed and released to the ON position, the PTO
relay will be energized by the PTOM. The cruise control
SET and RES + switches are used to control PTO
desired speed. Note that the cruise control ON/OFF
switch shall be set to OFF for PTO to operate.
PTO Telltale Indicator
The PTO telltale indicator is a part of the DIC message
center. The PTOM shall command the state of the PTO
telltale via instrument panel displays based on the
following criteria:
The telltale will illuminate, flashing at a 0.5 second
interval rate when the PTO relay is energized. The
indicator illuminates solid once the PTO load
feedback signal confirms the load has been
engaged or after 2 seconds if load feedback is not
utilized by the PTO system.
The telltale will flash at a 1 second interval rate
when PTO memory speed is retained. Depressing
the in-cab PTO switch to the OFF position turns
the PTO system off. The PTO telltale will turn off
once engine speed reaches base engine idle, at
which time the PTO relay is de-energized.
Power Take-Off Module (PTOM)
Processes PTO operator switch inputs and
translates these inputs into an engine speed
request to the ECM
Controls the engagement of the PTO load relay
Process requests to the BCM and ECM to start
and shutdown the engine
Requests the IPC to display on the DIC the
actions the driver must take to enable PTO
Requests the ECM to command an engine
shutdown and engine shutdown horn warning for
critical engine and transition conditions (stationary
remote PTO only).
The PTOM constantly looks at the information from
various sensors and other inputs, and controls the
systems that affect vehicle performance. If any of the
PTO engage conditions for the specific operating mode
are no longer valid, the engine controller will exit out of
PTO mode.
Remote PTO Upfitter Connector
The PTO upfitter connector provides access to all
remote PTO functions. The connector is located on the
right-hand outside frame rail, underneath the
passenger side door. Electrical connections to the
following components are provided by this connector.
The upfitter connector pin circuits (other than battery,
ignition and ground) are disabled as the vehicle is
received from the factory. The PTO module must be
reprogrammed by the upfitter or dealer to enable the
following circuits:
PTO remote engine arm
PTO remote engine shutdown/start
PTO remote set/variable speed potentiometer
and
PTO lead feedback
Other Vehicle Modules
The PTO system also utilizes the following vehicle
modules, which communicate over the serial data
system:
The body control module (BCM)
The engine control module (ECM)
The instrument panel cluster (IPC)
The transmission control module (TCM)
The electronic brake control module (EBCM)
Body Control Module (BCM)
The BCM maintains the PTO factory default mode,
unless it is reprogrammed with a scan tool to change
the PTO configuration mode. The BCM also controls
the remote start/shutdown function.
Engine Control Module (ECM)
The ECM controls the engine speed and the engine
starting based on messages from the PTOM through
serial data. The ECM also provides PTO specific
engine information to the PTOM through serial data
messages.
Electronic Brake Control Module
The EBCM monitors the vehicle speed. The PTOM
receives the status of the vehicle speed from the EBCM
via serial data messages.
Instrument Panel Cluster (IPC)
The driver information center (DIC) of the IPC displays
actions the driver must take in order to engage PTO.
If the PTO will not engage, one or more of the following
DIC messages may appear on the instrument panel
cluster (IPC):
2021 - Silverado 4500HD, 5500HD, and 6500HD Electrical Body Builder Manual