C 3500 HD Truck 2WD V8-8.1L VIN G (2002)
Power Take-Off: Description and Operation
General Information
The PTO is an Upfitter integrated system that allows the user to create an auxiliary power source that will drive either a hydraulic pump or a generator.
When the operator requests PTO the PTO switch will be turned ON and the engine RPM will go to a default standby speed. The operator will then press
and release the PTO switch to SET and the PTO solenoid will engage. Turning the PTO switch to OFF or pressing the brake pedal will turn the PTO off.
The PTO system is integrated with the Cruise Control system and Computers and Controls Systems. The PTO system utilizes the following parts:
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PTO Switch
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Cruise Control Multi-Function Switch
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PTO Relay
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PTO Solenoid
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PCM
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TAC Module
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TAC Motor
Voltage will be supplied at all times through the Fog Lamp fuse to the secondary side of the PTO Relay. When the operator turns the ignition switch to
RUN, voltage will be supplied through the Cruise fuse to the open PTO switch.
When the PTO switch is turned to ON voltage will be present through the primary side of the PTO Relay and at the PCM.
If the PCM sees all of the requirements for PTO engagement the PCM will send a Class 2 signal to the TAC Module. The TAC Module will use the TAC
Motor to increase the engine RPM to the standby speed. When the PTO switch is turned to the SET position and then released the PCM will ground the
primary side of the PTO Relay. Current will flow through the coil in the PTO Relay and close the normally open contacts. This will allow current to flow
to the PTO Solenoid and eventually to ground.
In the event that any of the PTO requirements are no longer met then the PCM or TAC will return the engine RPM to idle and turn the PTO Solenoid off.