On-Highway Engines Electronic PTO Installation and Application Guide Caterpillar

Switch Electrical Specifications

The plating that is on the switch should not corrode and the plating should not oxidize. Gold plated contacts are recommended. All switches should be an environmentally sealed unit. All switches should be protected according to the requirements of the application.

Normally, the applied voltage to the switches will not exceed 11.5 Volts. The normal current draw through the switches will not exceed 0.0065 Amp (6.5 mA).

The chatter (momentary opening and closing) of the contacts should not exceed a duration of 0.1 seconds (100 milliseconds). The switches should not open and the switches should not close due to a vibration or shock. Closure of an installed switch must short the circuit. The input will short to the Input Sensor Common 1 (terminal 18) or to the Input Sensor Common 2 (terminal 3) of the J1/P1 Engine Control Module (ECM) Vehicle Harness Connector.

Voltage Thresholds (Measurement at the ECM)

Voltage Input of Less Than 0.9 Volts - When the switch contacts close, the voltage that is across the following items must be less than 0.9 Volts between the respective control input and the sensor common connection: difference of the ground potential, drop in switch voltage and drop in voltage for the wiring harness.

Voltage Input Equal To or Greater Than 4.0 Volts - When the switch contacts open, the following items must not result in an effective resistance of less than 5,000 Ohms from the respective control input to the sensor common connection: the pin to pin leakage paths in connectors, harnesses and switches.

Note: The following terminals are designated as the Sensor Common connection J1/P1: Terminal 3 (Input Sensor Common 2) and terminal 18 (Input Sensor Common 1). OEM installed switches that are input into the ECM must not be connected to the vehicle or to the cab ground. The OEM installed switches must be grounded to the Sensor Common by using a dedicated return line to ECM Vehicle Harness Connector P1.

Selecting a Switch Type

The type of switch that is required depends on the type of application that is required. The Cruise Control Set/Resume or the RPM Increase/RPM Decrease Switch is typically a three-position momentary switch. A spring is used in order to return the switch to the OFF position.

The PTO On/Off Switch can be an On/Off or a two-position switch. The switch can be actuated by one of the following operations:

• Manual

• Air

• Hydraulic

The Interlock Switches for the PTO are typically actuated by air. The Interlock Switches for the PTO are also in the normally closed position. The switches are connected into the air lines for the Parking Brake or connected to the air lines for the Transmission. All switches may be controlled hydraulically or the switches may be limit switches. All switches that are located outside the cab should be environmentally sealed and protected.

Switches That Are Available from Caterpillar

A 112-4073 Pressure Switch Gp is available. The switch has the following features: single pole, single throw and actuated by air.

Illustration 1	g00621900
Schematic for the 112-4073 Pressure Switch Gp The actuation pressure for the switch is the following value: 330 kPa (48 psi)

Electrical Specifications for the Remote Accelerator Pedal Position Sensor

The accelerator pedal position sensor is required. Refer to the Parts Manual for your engine for more information. The sensor is supplied with a Deutsch HD connector. The Deutsch part number is HD16-3-96S. The Caterpillar part number is 8T-8731 Connector Plug. The connecting harness will require a Deutsch HD receptacle connection. The Deutsch part number is HD14-3-96P. The Caterpillar part number is 8T-8732 Receptacle .

Note: The accelerator pedal position sensor can not be powered by the 8 Volt power supply from the ECM. The accelerator pedal position sensor must be connected and powered by 12/24 Volt battery voltage.

Mounting the Accelerator Pedal Position Sensor

Illustration 2	g00638606
107-2281 Mounting Block As The handle is not included.

The accelerator pedal position sensor can be attached to either an accelerator pedal assembly or a 107-2281 Mounting Block As. The PTO accelerator assembly does not include the handle. A mechanical linkage can also be used in the application. Contact the vehicle OEM in order to obtain information on the part number for the accelerator pedal assembly.

Illustration 3	g00638604
Williams Controls, Inc. Pedal assembly

Note: The accelerator pedal position sensor 161-8906 Position Sensor Gp provides a Pulse Width Modulated signal to the ECM that is constant frequency. The duty cycle varies with the position of the accelerator pedal. The "ECM Remote Throttle" input cannot be used with a vernier control cable assembly or as an input for the throttle switch. The "ECM Remote Throttle" input must receive the correct PWM signal while the ECM is powered up. Also, the "ECM Remote Throttle" input must receive the correct PWM signal when the "PTO Configuration" is programmed to "Remote Throttle", or when a diagnostic code is logged or active.

Specifications for the Harness

The harness should be protected from the environment by using a conduit that is plastic or by other means. All of the wire for the harness should be 18 AWG or the wire should be larger. The wire for the harness should be SAE J1128. The wire for the harness should be SXL or GXL. Use an equivalent wire for the harness if one of the types is not available. The acceptable range for wire insulation outside diameter is 2.26 to 3.33 mm (0.089 to 0.131 inch). All ring terminals and all splices that are connected to the harness must be sealed. All ring terminals and all splices that are routed to the engine ECM must be sealed. Seal the terminals and splices with Raychem ES2000 heat shrink tube or the equivalent in order to seal the ring terminals and the splices.

Illustration 4	g01114788
(1) Contact Pin (2) Machined socket contact (3) Stamped and forged socket contact (4) Sealing plug