HOSE AS 5088348 - Caterpillar

Illustration 1 g00288430
Typical square wave pulse width modulated duty cycle signalA position sensor will continuously send a square wave pulse width modulated signal to an ECM. The frequency of the signal is usually 500 Hz, however, some sensors operate at 5000 Hz. The operating frequency remains at a steady rate during operation. During operation, the duty cycle of the PWM sensor signal changes. The change depends on the following:
Direction of movement about the axis that is being monitored
Amount of movement about the axis that is being monitoredThe duty cycle is the percentage of time that the signal is high, compared to the total time of the cycle.The duty cycle has the following characteristics:
Percentage of duty cycle signal recognized as valid by ECMs is 10 5 percent to 90 5 percent. An axis that is in the center or neutral position would result in a duty cycle signal of approximately 50 6 percent.The sensor signal has the following characteristics:
The sensor signal can also be measured as voltage. Most PWM sensor signals will measure an RMS (average) voltage of between 0.0 VDC to 5.0 VDC depending on the duty cycle value. A low duty cycle results in a low voltage measurement. A high duty cycle results in a higher voltage value. ECMs will accept a duty cycle of 10 5 percent to 90 5 percent. This range equates to 0.5 VDC to 4.5 VDC.
To aid in ECM circuit diagnostics, all of the PWM sensor signal input circuits have an internal pull up voltage. An above normal voltage is internally connected to the ECM sensor PWM signal input circuit through a resister.
During normal operation, the sensor signal will hold the circuit at a certain signal amplitude. However, conditions such as power loss, disconnection, or open will allow the circuit to be pulled high by the ECM pull up voltage. This action results in an above normal voltage condition at the ECM contact. As a result, the ECM will activate a diagnostic code for the affected circuit. When the ECM detects an abnormal condition in the circuit, the ECM activates a diagnostic code for the PWM sensor signal circuit. The ECM will most often monitor the circuit for the following FMI conditions:FMI 02 - Erratic data, intermittent data, or incorrect dataFMI 03 - Voltage above normalFMI 04 - Voltage below normalFMI 08 - Abnormal frequency, pulse width, or periodFMI 13 - Out of calibrationNote: The ECM may activate diagnostic codes for FMI conditions that are not listed here. The FMI conditions that are listed here are the most common FMI conditions.When an FMI 13 is activated, a calibration procedure must be performed to maximize performance in the involved system.The sensor PWM duty cycle can be measured with most digital multimeters. The duty cycle should be in the acceptable range. The voltage of the signal circuit can also be measured. Most signals from PWM sensors are measured as "Duty cycle percentage".For information on a specific machine PWM position sensor,