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 Engine Controls. The PTO system utilizes the following parts:

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 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 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.

PTO -- Preset Mode (Factory Default Setting)

The PTO preset mode is used for stationary applications. PTO will remain engaged while mobile in the preset mode however PTO Preset 1 and PTO Preset 2 speed controls will be inoperative. The engine RPM will also return to normal. This mode provides a default standby speed of 800 or 850 RPM depending on the engine and transmission combination. This mode also provides 2 default PTO control speeds: PTO Preset 1 of 1250 RPM and PTO Preset 2 of 1700 RPM. Please note that the standby speed is not to be used as a PTO control speed. Vehicles not equipped with cruise control will not have the resume speed capability.

PTO -- Variable Mode

The PTO speed control mode is used for both stationary and mobile applications. This mode allows PTO to be controlled in a fashion similar to cruise control. The operator is able to hold an engine RPM between 800 and 2200 with the SET switch on the cruise stock or the PTO switch. The operator can "tap up" to increase engine speed in 100 RPM increments with the RESUME switch. The operator may also "tap down" to decrease engine speed with either SET switch on the cruise control multifunction switch or the PTO switch. Vehicles not equipped with cruise control will not have the "tap up" capability.

PTO Switch

The PTO Switch is mounted in the center of the Instrument Panel. The PTO Switch has three positions: OFF, ON and SET. When the PTO switch is in ON voltage will be present on the PTO On Switch Signal circuit at the relay and the PCM. When the switch is held to the SET position, voltage will be present on the PTO Engage Signal circuit at the PCM. The PTO indicator light is integral with the switch and will illuminate when the switch is turned ON. The presence of the indicator being on does not mean that the PTO Solenoid is engaged. The Cruise Control Multi-Function Switch may be used in conjunction with the PTO Switch. Illumination of the switch is provided through the dimming circuit and controlled in part by internal switch logic.

Cruise Control Multi-Function Switch

The operation of the PTO system may be through the function control switches located on the multifunction turn signal lever. The cruise control function control switches includes the ON/OFF, SET/COAST, and R/A. The switch assembly provides driver control of the PTO as well as the cruise control system. The SET/COAST and R/A switches may be used to increase and decrease engine RPM in increments of 100 RPM. See the chart below for recommended speeds.

PTO Relay

The PTO Relay is located on the side of the underhood fuse block. The secondary side of the relay is supplied with voltage at all times through the Fog Lamp fuse. The PTO switch controls the voltage to the primary side of the PTO relay while the PCM controls the ground.

PTO Solenoid

The solenoid is an upfitter supplied part and is replaceable on most PTOs. The PTO solenoid is used on clutch activated PTOs. The PTO relay supplies the solenoid with voltage when the relay is energized.

PCM

The powertrain control module (PCM) is the control center of the PTO system. Applications with a 6.6L diesel use an ECM. The PCM monitors numerous engine and vehicle functions. To engage the PTO, the PCM must see the following conditions:

The PCM constantly looks at the information from various sensors and other inputs, and controls the systems that affect vehicle performance. The PCM also performs a diagnostic test on the Electronic Throttle Control system.

TAC Module

The TAC module is the control center for the electronic throttle system. The TAC module and the PCM communicate through a dedicated redundant serial data circuit. The TAC module and the PCM monitor the commanded throttle position and compare the commanded position to the actual throttle position. This is accomplished by monitoring the APP and the throttle position (TP) sensor. These 2 values must be within a calibrated value of each other or a DTC may be set. The TAC module also monitors each individual circuit of the TP sensor and the APP to verify proper operation. The TAC module commands the TAC motor to increase or decrease the engine RPM.

TAC Motor

The TAC motor is part of the throttle body and controls the positions of the throttle. The motor is bi-directional and is controlled by the TAC module. The TAC motor increases or decreases the engine RPM.