PICK-UP A 4W7244 - Caterpillar

Left Travel Pressure Switch and Right Travel Pressure Switch
The left travel pressure switch and right travel pressure switch detects a travel operation. The travel pressure switches send an input signal to the machine ECU. The machine ECU uses the switch information to control the engine speed and pump control.Outputs
The ECU responds to decisions by sending electrical signals to the outputs. The outputs can create an action or the outputs can provide information to the operator or the service technician.Solenoids
On/Off Solenoids
Illustration 7 g01158530The values in Table 7 are for bench testing only. Values may not represent parameters for machine systems specifications.
Table 7
Rated Voltage 24 VDC
Coil Resistance 32.0 3.2Ω (T=20° C) The On/Off solenoids include:
Travel speed solenoid
Straight travel solenoid
Hydraulic lock solenoidTravel Speed Solenoid
The travel speed solenoid is an output of the Machine ECU. When the travel speed solenoid is active, the machine can travel at high speed. The travel speed solenoid is active when the travel speed mode switch is set to "RABBIT (high)" mode. The travel speed also depends on the delivery pressure of the main pump. If the delivery pressure of the main pump is high, the travel speed solenoid is de-energized. When the delivery pressure of the main pump is low, the travel speed solenoid is energized.Straight Travel Solenoid
The straight travel solenoid is energized to maintain straight travel even though a swing operation or implement operation is performed during travel.The straight travel solenoid ensures straight travel of the machine when other circuits are operated during travel. The machine ECU recognizes the input status of the right travel pressure switch, left travel pressure switch, and the implement pressure switch. When all three pressure switches are activated to the ON position, the machine ECU activates the straight travel solenoid. Straight travel is now maintained.For more information on the straight travel solenoid, refer to Systems Operation, "Control Valve (Straight Travel)".Hydraulic Lock Solenoid
The hydraulic lock solenoid is an output of the Machine ECU. The hydraulic lock solenoid is energized in order to enable the primary hydraulic pressure. The hydraulic lock solenoid is de-energized in order to disable the primary hydraulic pressure.This solenoid is activated while the key switch is in the ON position and the hydraulic lock lever is in the UNLOCK position.Proportional Reducing Solenoid Valve
Illustration 8 g03462498The values in Table 8 are for bench testing only. Values may not represent parameters for machine systems specifications.
Table 8
Current Range 0 mA ~ 700 mA
Coil Resistance 11.5 0.5Ω (T=20° C)
Illustration 9 g03462556
A - Port pressure (kPa) vs Current (mA)
The P-Port is blocked and does not allow pressure to the A-port. Therefore, the machine ECU must apply current to the PRV in order to sent pressure to the A-port of the PRV.The PRV's include:
Negative Flow Control 1 Limit PRV
Negative Flow Control 2 Limit PRV
Power Shift Pressure PRVNegative Flow Control 1 Limit PRV and Negative Flow Control 2 Limit PRV
Two proportional reducing valves for negative flow control are used to control the amount of NFC signal to the pump regulators. The machine ECU receives various input