BAND-MOUNTING 1524891 - Caterpillar

Machine ECM
The machine ECM is the control module that will use the programmed control logic to manage the operation of most of the machine functions. The machine ECM will use the data from the various input devices to determine the appropriate output response to operator commands.The machine ECM determines all of the appropriate output commands and communicates this information to the Implement ECM on the SAE J1939 (CAN) data link.The machine ECM will activate outputs in order to energize or de-energize solenoids that will control the installed machine functions.
Illustration 6 g03701879
Machine ECM connectors
(1) J1 connector
(2) J2 connector Pin Locations for Machine ECM
Illustration 7 g03701995
Machine ECM connector (70-pin)
Table 2
Machine ECM - J1 Contact Connections
Pin Location Function Description
16 Fan speed sensor Analog input
69 Fan speed sensor supply voltage (10 VDC) Sensor power supply 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