Advantages of a Dedicated PTO
The ECM provides several options in order to enhance vehicles that require control of the engine speed for vocational applications. The vocational applications include the following applications: cement mixers, refuse packers, bulk haulers, utility trucks, fire trucks and applications that require the control of the engine rpm for the operation of specialized equipment.
There are 15 dedicated PTO parameters. The dedicated PTO has seven inputs and one output. The features of the dedicated PTO provide a significant increase in the capability of the engine and of the usage of the engine.
An electronically controlled engine eliminates the need for the following items: mechanical control cables, air cylinders, electric solenoids and linkages and connections. The dedicated PTO provides a simple installation. The Cruise Control switches that are in the cab and the circuit for the accelerator pedal position are left unaffected.
Features of the Dedicated PTO
There are several features of the dedicated PTO:
- The dedicated PTO reduces the alteration of the cab wiring or the dedicated PTO eliminates the alteration of the cab wiring.
- The dedicated PTO has multiple speed control by using the "PTO Engine RPM Set Speed A" and "PTO Engine RPM Set Speed B".
- The dedicated PTO has two speed controls that require the PTO On/Off circuit.
- The dedicated PTO provides three different PTO configurations which determine the operation of the dedicated PTO.
- The dedicated PTO has one speed control that has a programmed low idle to PTO set speed for engine rpm with one circuit.
- The dedicated PTO has two speed controls with three circuits. The three circuits are the "programmed low idle", the "PTO preset set speed", and the "PTO TEL".
- The accelerator pedal in the cab can be disabled without altering the cab wiring.
- The dedicated PTO provides an rpm limit for the accelerator pedal in the cab and the cab switches.
- The dedicated PTO has additional inputs for the remote accelerator position sensor. The remote accelerator position sensor provides control of the engine rpm on the outside of the cab.
- The dedicated PTO has additional Set/Resume inputs for control of the engine rpm. The inputs can be remote. An example would be outside of the cab.
- "Engine set speeds" that are lower can be used to reduce the level of engine noise during dedicated PTO operation. "Engine set speeds" can be lower than a mechanical engine.
- The ECM controlled Engine Retarder is disabled when the PTO On/Off switch is in the ON position.
- The idle shutdown feature is disabled when the PTO On/Off switch is in the ON position.
- The dedicated PTO provides a programmable "PTO shutdown time" in order to reduce driver abuse. Driver abuse is placing the truck in dedicated PTO mode in order to disable the "idle shutdown timer".
- The cab clutch inputs and the service brake inputs can be prevented from disengaging an "engine set speed" during dedicated PTO operation. Slow moving vehicle operations require control of the engine rpm from the cab. An example would be a curb pouring cement truck.
- The dedicated PTO provides a programmable "engine torque limit".
- The dedicated PTO provides a programmable "engine rpm acceleration/deceleration ramp rate" and a programmable "engine rpm bump rate".
- The dedicated PTO requires an OFF and ON transition of the PTO On/Off switch in order to begin dedicated PTO operation.
- The dedicated PTO provides the ability to keep the ECM controlled cooling fan "ON" during dedicated PTO operation.
Customer Programmable Parameter Options
There are many customer programmable parameter options:
"PTO Configuration" - The "PTO Configuration" determines the input/output configuration that is used for the Dedicated PTO operation.
"PTO TEL" - The "PTO TEL" provides a parameter in order to limit the engine rpm during PTO operation.
"PTO Engine RPM Set Speed" - The "PTO Engine RPM Set Speed" provides a set point for the engine rpm for the PTO.
"PTO Engine RPM Set Speed A" - This provides a programmable engine speed set point that is actuated by a dedicated switch circuit. The dedicated switch circuit is Input 7.
"PTO Engine RPM Set Speed B" - This provides a second programmable engine speed set point that is actuated by a second dedicated switch circuit. The dedicated switch circuit is Input 19.
"PTO to Set Speed" - The "PTO to Set Speed" function requires only one circuit (PTO On/Off Switch) to provide two speed controls. The "PTO to Set Speed" function provides three-speed controls by using the PTO On/Off Switch and the Set/Resume Switch.
"PTO Cab Controls RPM Limit" - The "PTO Cab Controls RPM Limit" provides a parameter in order to limit the rpm from the accelerator pedal position sensor in the cab during PTO operation. The "PTO Cab Controls RPM Limit" can be used in order to exceed the programmed "PTO TEL" with the accelerator pedal that is in the cab.
"Torque Limit" - The "torque limit" reduces the engine torque during PTO operation. The "torque limit" will also reduce the engine torque when the Torque Limit Switch is in the ON position for temporary protection of equipment.
"PTO Vehicle Speed Limit" - The "PTO Vehicle Speed Limit" determines the operating range of the vehicle speed during PTO operation.
"Idle/PTO RPM Ramp Rate" - The "Idle/PTO RPM Ramp Rate" determines the rate of acceleration and deceleration.
"Idle/PTO Bump RPM" - The "Idle/PTO Bump RPM" determines the amount of change in the engine rpm when the Set/Resume Switch is toggled.
"PTO Shutdown Time" - The "PTO Shutdown Time" is a programmable time. If the engine is in PTO mode, then the "PTO Shutdown Time" will shut down the engine when the time limit expires.
"PTO Activates Cooling Fan" - The "PTO Activates Cooling Fan" can be programmed so that the cooling fan will operate during PTO operation.
"Input 4" - "Input 4" provides a parameter for a Torque Limit Switch when torque limiting is desired for temporary protection of equipment. This is regardless of the position of the PTO On/Off switch. MAR98 or later Personality Modules
"Input 5" - "Input 5" provides a parameter for an Ignore Brake/Clutch Switch when mobile use of the vehicle is desired with a set engine rpm. The brake and the clutch are not required in order to disengage the engine rpm set speed. MAR98 or later Personality Modules
"Input 7" - "Input 7" can be programmed to "PTO Engine RPM Set Speed A" in order to provide a dedicated circuit for the PTO operation at a programmed speed when the PTO On/Off Switch is ON. JUL99 or later Personality Modules
"Input 19" - "Input 19" is programmable to "PTO Engine RPM Set Speed B" in order to provide a second dedicated circuit for the operation at a programmed speed when "PTO Engine RPM Set Speed A" is OFF and the PTO On/Off switch is ON. JUL99 or later Personality Modules
"Torque Limit Switch" - The "torque limit switch" parameter limits torque regardless of PTO operation.
"Ignore Brake/Clutch Switch" - The "ignore brake/clutch switch" parameter allows mobile use of the vehicle during PTO operation. The "ignore brake/clutch switch" parameter allows mobile use of the vehicle when an "engine rpm set speed" is required and the brake or the clutch is not required in order to disable the "engine rpm set speed".
"Cruise/Idle/PTO Switch Configuration" - The "Cruise/Idle/PTO switch configuration" determines if the set switch or the resume switch will function as the "ACCEL" or the "DECEL" function.
"PTO Switch On Lamp" - The "PTO switch On lamp" parameter allows a lamp to illuminate when the PTO On/Off switch is in the ON position.
Additional Features of the Dedicated PTO
- When the PTO On/Off switch is in the ON position, the Idle Shutdown feature is disabled.
- Two terminal connector and wiring is standard for the PTO On/Off Switch. Two terminal connector and wiring is standard for the PTO Interlock Switches.
- The PTO Shutdown Timer reduces driver abuse. Driver abuse is placing the truck in PTO mode in order to disable the idle shutdown time.
Definition of Power Take-Off (PTO)
The dedicated PTO is an engine rpm control that is initiated through an On/Off circuit. The circuit is connected to Input 1 (terminal 56) of the ECM Vehicle Harness Connector J1/P1. Engine rpm control that is initiated through the Cruise Control On/Off switch is referred to as Extended Idle. Engine rpm control that is initiated through the Fast Idle Enable Switch is referred to as Fast Idle.
The Four Programmable PTO Configurations
"Off" - The functions for the dedicated PTO are not available.
"Cab Switches" - The cruise control Set/Resume switch and the Accelerator Pedal are used to control the engine rpm. A dedicated PTO On/Off switch is required. Refer to Illustration 1.
"Remote Switches" - The Set/Resume switch for the remote PTO is used to control the engine rpm. The "Remote Switches" configuration ignores all of the cab controls. An On/Off switch for the dedicated PTO is required. Refer to Illustration 2.
"Remote Throttle" - The "Remote Throttle" configuration is used in order to control the engine rpm. The "Remote Throttle" configuration will ignore all of the cab controls. An On/Off switch for the dedicated PTO is required. Refer to Illustration 3.
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| Illustration 1 | g00625394 |
"Cab Switches" PTO configuration (1) Cruise Control Set/Resume Switch (2) PTO On/Off Switch (3) PTO Switch On Lamp | |
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| Illustration 2 | g00625393 |
"Remote Switches" PTO configuration (4) PTO Switch On Lamp (5) PTO Set/Resume Switch (6) PTO On/Off Switch (7) PTO Switch On Lamp | |
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| Illustration 3 | g00625391 |
"Remote Throttle" PTO configuration (8) PTO Switch On Lamp (9) PTO On/Off Switch (10) PTO Set/Resume Switch (11) PTO Switch On Lamp (12) Remote Throttle for the PTO | |
One Speed Control with One Circuit
One speed control with one circuit provides an optional PTO Set Speed for applications that require only one speed above low idle. The following components are required: PTO On/Off Switch, PTO Interlock Switches and PTO Switch On Lamp(s).
Two Speed Control with Three Circuits
The two speed control with three circuits has two set speeds above low idle. The two set speeds that are above the low idle engine rpm are the PTO to Set Speed and the PTO TEL. The following components are required: PTO On/Off Switch, PTO Interlock Switches, Cruise Control or Remote Set/Resume Switch and PTO Switch On Lamp(s).
Variable Speed Control that uses "Remote Switches"
The following components are required: PTO On/Off switch, PTO interlock switches, PTO Set/Resume switch and PTO switch On lamp
Variable Speed Control that uses an Input for the Remote Accelerator Position Sensor
The following components are required: PTO On/Off Switch, PTO Interlock Switches, Cruise Control Switch or Remote Set/Resume Switch and Remote Hand Accelerator or an Accelerator Pedal Assembly that is equipped with an Accelerator Position Sensor that is supplied by Caterpillar.
Multiple Speed Control That Uses Dedicated Switch Inputs
This function can be used in conjunction with other features that are used to control engine speed. The function is available for the three configurations for the PTO. The following components are required: PTO On/Off Switch, PTO Interlock Switches and switch for the "PTO Engine RPM Set Speed A". The switch for the "PTO Engine RPM Set Speed B" can be used in addition to the switch for the "PTO Engine RPM Set Speed A".
Engine RPM Control That Uses Switches Instead of a Control That Uses An Accelerator Position Sensor
This function uses switches in order to control engine rpm. Switches are also recommended if the operator of the PTO will be frequently varying the engine rpm. Switches are recommended if the operator of the PTO will not have a free hand or a free foot in order to operate the accelerator.
Recommended Information for Operator of the PTO
Ensure that the operator understands the operation of the engine and the components for the PTO operation. Ensure that the operator understands the operation before attempting to install the switches before the parameters are programmed. The installation questionnaire will make the installation easier to understand. The installation questionnaire will help the installer understand the options that are needed.
Question (1) through question (8) should be asked before starting the installation procedure. The remaining questions may be asked after the installation is completed. This will help to fine tune the programming and other system components. Refer to the information for programmable parameters that is found in "Programmable Parameters Available Ranges, Options, and Default Settings". For more information, refer to Special Publication, LEXT0023, "Programming CAT Electronic Truck Engines". Also refer to Special Publication, LEBT9390, "Electrical and Electronic Application and Installation Guide".
Complete the following information once the installation is complete:
- Programmed Parameter Information Sheet for the Operator of the PTO
- Instructions for the Operator of the PTO
- Diagrams for Switches and Components that are used for the Installation of the PTO
The information that is recorded should be explained to the operator of the PTO. The information that is recorded should be left in the cab glove box. This will allow the operator of the PTO to review the configuration of the truck and the PTO. This will allow the service technician to troubleshoot any suspected problems that relate to the installation.
Installation Questionnaire
Refer to the C-10, C-12, 3406E, C-15, C-16 Truck Engines Electronic PTO Installation and Applications Service Manual, "PTO Parameters - Program" for the installation and programming that is based on the information on the Questionnaire Response.
| Questions | Response |
| Determine the location of the controls inside the cab for the PTO. Determine the location of the controls outside the cab for the PTO. Determine if control of the engine rpm is required from both the cab and outside of the cab. Determine if the operator of the PTO will be continually varying engine rpm. Determine if a hand accelerator or a foot accelerator will be used. |
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| Determine the maximum PTO operation vehicle speed. Determine if the PTO will require the use of the clutch and the service brakes. Determine that the engine rpm must be maintained when the clutch and service brakes are used. |
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| Determine the maximum torque of the equipment when the PTO On/Off circuit is ON. | |
| Determine the necessity of a torque limit when the PTO On/Off circuit is in the OFF position. Example Determine that a torque limit is needed in order to reduce the torque for the driveline. |
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| Determine if one or more fixed engine rpm above low idle is required. Determine the first engine rpm. Determine the second engine rpm. Determine the necessity in order for the engine to accelerate to the first engine rpm when the PTO On/Off switch is turned to the ON position. |
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| Determine the operating speed points. | |
| Determine the maximum operating engine rpm for the equipment. Determine if the accelerator pedal rpm should be limited. This will occur only if the control of the engine rpm is from the cab. |
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| Determine the acceleration rate that is required in order for the engine to reach the set point for the engine rpm. Determine the rate of deceleration that is required in order for the engine to decelerate from the set point for the engine rpm. | |
| Ask the following question ONLY if the vehicle uses the Caterpillar Engine Control Module (ECM) to turn the engine cooling fan ON. If necessary, contact the OEM of the vehicle for more information. Determine the minor fluctuations in engine rpm that are caused by the engine cooling fan that is cycling ON and OFF. Determine if this will cause a pump problem or other system problems. |
Programmed Parameter Information Sheet for the Operator of the PTO
Use the following table to fill in the programmed parameters once the installation is complete. Otherwise, print a copy of the engine configuration by using the Electronic Technician.
| "Selected Engine Rating" | |
| "Rating Number" | |
| "ECM Identification Parameters" | |
| "Vehicle ID" | |
| "Truck Manufacturer Parameters" | |
| "Truck Manufacturer" JUL99 and newer Personality Modules |
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| "Vehicle Speed Parameters" | |
| "Vehicle Speed Limit" | |
| "Cruise Control Parameters" | |
| "Low Cruise Control Speed Set Limit" | |
| "High Cruise Control Speed Set Limit" | |
| "Cruise/Idle/PTO Switch Configuration" | |
| "Idle Parameters" | |
| "Idle Vehicle Speed Limit" | |
| "Idle RPM Limit" | |
| "Idle/PTO RPM Ramp Rate (rpm/sec)" | |
| "Idle/PTO Bump RPM" | |
| "Fast Idle RPM 1" | |
| "Fast Idle RPM 2" | |
| "Dedicated PTO Parameters" | |
| "PTO Configuration" | |
| "PTO TEL" | |
| "PTO Engine RPM Set Speed" | |
| "PTO Engine RPM Set Speed A" | |
| "PTO Engine RPM Set Speed B" | |
| "PTO to Set Speed" | |
| "PTO Cab Controls RPM Limit" | |
| "PTO Vehicle Speed Limit" | |
| "Torque Limit" | |
| "PTO Shutdown Time" | |
| "PTO Activates Cooling Fan" | |
| "Engine and Gear Parameters" | |
| "TEL" | |
| "Low Idle Engine RPM" | |
| "Transmission Style" | |
| "Input Selections" | |
| "Input Number 4" (Torque Limit Switch) | |
| "Input Number 5" (Ignore Brake/Clutch Switch) | |
| "Input Number 7 (PTO Engine RPM Set Speed A)" | |
| "Input Number 19 (PTO Engine RPM Set Speed B)" | |
Instructions for the Operator of the PTO
| Question | Response |
| The following interlocks must be set before the engine can be operated for PTO purposes. For example, the parking brake must be engaged and the transmission must be placed in the neutral position. |
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| Determine the location of the PTO On/Off switch. Determine the labeling of the switch. | |
| Determine the maximum vehicle speed while the PTO is in operation. NOTE: Exceeding the maximum vehicle speed will cause the engine to exit the PTO set speed. The engine will then return to low idle. |
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| Determine if the PTO is set up to allow the use of the clutch and service brakes with an engine rpm set speed. Determine the PTO mode vehicle speed limit that is required for the operation of the PTO. If the answer is yes, then determine the location of the switch that allows this operation. Determine the labeling of the switch. |
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| Determine the acceleration rate that is required in order for the engine to reach the set point for the engine rpm. Determine the rate of deceleration that is required in order for the engine to decelerate from the set point for the engine rpm. | |
| Determine if only one or two engine rpm above low idle are necessary. Determine the first engine rpm. Determine the second engine rpm. |
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| Determine if the installation is configured for engine acceleration to increase to a desired engine rpm. This should happen when the PTO On/Off switch is turned to the ON position. | |
| Determine the necessity that involves the cooling fan that runs constantly when the control that is for the cooling fan is active. | |
| Determine the location of the PTO Switch On Lamp. Determine the labeling of the switch. | |
| Determine the programming of the "PTO Shutdown Timer". | |
| Determine the programming of the "PTO Torque Limit". |
Truck Installation Diagram for The Switches and The Components
Follow the steps below once the installation is complete:
- Locate the following items and create a sketch of these items: switches, sensors and lamps. Refer to the C-10, C-12, 3406E, C-15, and C-16 Truck Engines Electronic PTO Installation and Applications Service Manual, "The Four Programmable PTO Configurations" for the installation and programming that is based on the information on the Questionnaire Response.
- Provide a copy of the appropriate diagrams from this manual that illustrate the specific installation to the vehicle owner.
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| Illustration 4 | g00720254 |
(1) Torque limit switch (2) Ignore/Normal Brake/Clutch switch (3) PTO On/Off switch (4) PTO switch On lamp (5) PTO Set RPM Increase/Set RPM Decrease switch (6) PTO accelerator assembly (7) PTO switch On lamp (8) PTO Engine RPM Set Speed A On/Off switch (9) PTO Engine RPM Set Speed B On/Off switch | |