HOSE RAD 1039952 - Caterpillar

Inputs
The inputs describe the status of the machine systems. Two types of inputs exist. The inputs can be either a switch type or a sensor type. Switches provide an open, a ground, or a + battery signal to the inputs of the controller. Sensors (frequency, PWM, or voltage) provide a changing signal to the sensor inputs of the controller.Sensor Inputs
Most sensor input circuits have an internal ECM "pull up voltage" that is present at the ECM contacts. An above normal voltage is internally connected to the ECM input circuit through a resistor. During normal operation, the sensor signal will hold the circuit at a certain signal amplitude. However, conditions such as a loss of power to a component, a disconnection, or an open circuit allow the circuit to be pulled high. The circuit is pulled high by the ECM pull up voltage. This situation will result in an above normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 03 (voltage above normal) diagnostic code for the affected circuit. The types of ECM input sensor circuits that have pull up voltage present are the following circuits:
Pulse Width Modulated (PWM) sensor input circuits
Active analog (voltage) input signal circuits
Passive analog (resistance) input signal circuitsPulse Width Modulated (PWM) Position Sensor OperationWhen powered up, the position sensors continuously send a Pulse Width Modulated (PWM) square wave signal to the ECM. Any movement on a specific axis is detected by the position sensor for that axis. The duty cycle of the PWM sensor signal changes depending on the direction and amount of movement on the axis. The duty cycle is the percentage of time that the signal is high verses the amount of time the signal is low for one cycle. The more time that the duty cycle is high, the greater the percentage of the duty cycle will be. The percentage of duty cycle signal for a typical position sensor will be recognized as valid is 10 5 to 90 5 percent. These percentages occur the extreme ends of the axis movement. A typical joystick thumbwheel that is in the center or neutral position would result in a duty cycle signal of approximately 50 5 percent. For a foot pedal that is not depressed, a typical duty cycle signal would be 10 5 percent. The duty cycle would be 90 5 percent when the pedal is depressed.The position sensors are calibrated by the ECM to relate a specific duty cycle signal to a specific axis position for the device being monitored. The ECM will convert the duty cycle from the position sensor to a calibrated duty cycle signal. The ECM uses this signal and a software "map" to determine the appropriate output signal that will be applied to an output device.Note: None of the PWM sensors on the M300F Series machines require manual calibration. The machine ECM will perform an automatic calibration procedure at ECM power up.The steering and brake system