PLATE & FILM GP 3156522 - Caterpillar

Inputs
The machine has several different types of input devices. The ECM receives machine status information from the input devices and determines the correct output action that is needed in order to control machine operations based on memory and software parameters. The machine utilizes the following types of inputs: switch type and sensor type. Switches provide signals to the switch inputs of the ECM. The possible outputs of a switch are listed: an open signal, a grounded signal and + battery signal. Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to the ECM can be one of several different types of electrical signals such as: pulse width modulated (PWM) signals, voltage signals and frequency input signals. Each possible input to the ECM is listed in the tables for the 70-pin connectors.Inputs provide information to the ECM in the form of sensors or switches.Sensors
Sensors provide information to the ECM about the intent of the operator or changing conditions. The sensor signal changes proportionally to the changing of operator input or changing conditions. The following types of sensor signals are used by the ECM.Frequency - The sensor produces a signal and the frequency (Hz) varies as the condition changes.Pulse width modulated - The sensor produces a signal. The duty cycle of the signal varies as the condition changes. The frequency of this signal is constant.Analog - The ECM measures the voltage that is associated to a specific condition of the control.Brake Charge Pressure Sensor
Illustration 3 g03324121The brake charge pressure sensor measures the pressure on the low side of the brake system. The sensor sends a pulse width modulated signal to the ECM. The duty cycle of the signal increases as pressure increases.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.Brake Pedal Switch
Illustration 4 g03571301The brake pedal switch is located in the base of the brake pedal assembly. The switch activates to illuminate the brake lights, and to alert the ECM that the service brakes are being applied. The switch has a normally open and a normally closed contact. When the switch is not activated, the normally open contact floats to a high voltage state, and the normally closed contact is pulled to a low voltage state. When the switch is activated the voltage state of the two contacts reverses.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 5 g03423744The brake charge solenoid is an on/off type solenoid that controls the flow of oil to the brake accumulators. The ECM sends a signal to energize or de-energize the