VALVE GP-PUMP CONTROL 2280391 - Caterpillar

Illustration 8 g03319963The brake oil temperature sensor is an active pulse width modulated sensor. The sensor changes the duty cycle as the temperature changes. A lower duty cycle represents a lower temperature and a higher duty cycle represents a higher temperature. The ECM interprets the duty cycle and is able to determine the temperature of the brake oil.Switches
Switches provide an open signal, a ground signal, or a +battery signal to the inputs of the ECM. Switches are open or closed.
When a switch is open, no signal is provided to the corresponding input of the ECM. This “no signal” condition is also called “floating”.
When a switch is closed, a ground signal or a +battery signal is provided to the corresponding input of the ECM.Parking Brake Switch
Illustration 9 g03431151The parking brake switch is a two pole switch. The switch has a common return for both poles of the switch, and three ECM contacts. Two of the contacts are on one pole and are a normally open and a normally closed contact. In the normally operating position, the normally open contact floats to a high voltage state and the normally closed contact is pulled to a low voltage state. The last ECM contact is an additional normally closed contact. When the switch is activated the normally closed contacts float to a high voltage state, and the normally open contact is pulled to a low voltage state. By monitoring the voltage state of the three ECM contacts, the ECM is able to determine the operator request for parking brake.Brake Pedal
Illustration 10 g03431189The brake pedal is a two pole limit switch, with the pedal change the state of the switch after being depressed. The first pole controls the brake lights and is directly connected to the switch. The contact for the light is normally open and is closed when the switch is depressed. The second pole alerts the ECM to the state of the brake pedal. The contact for the ECM is normally closed and opens when the pedal is depressed.Brake Charging Filter Bypass Switch
Illustration 11 g03424806The brake charging filter bypass switch is a single pole pressure switch. When the switch is closed under normal operation, the ECM contact is connected to a return contact. When the hydraulic pressure exceeds a set point, the switch opens. When the switch opens, the ECM contact floats to a high voltage from the ECM pull-up voltage. When the switch opens, the ECM alerts the operator that the brake charging filter is being bypassed.Outputs
The ECM 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
Brake Charge Solenoid
Illustration 12 g03423744The brake charge solenoid