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| Illustration 1 | g03702004 |
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Diagram of the machine control electronic communication system (1) Machine ECM (2) Implement ECM (3) Travel pedal (4) Engine ECM (5) CAN A data link (6) Machine monitor (7) Machine security system (8) CAN B data link (9) Operator control panel (10) Product link (11) Service connector (12) Communication adapter III (13) Electronic Technician (ET) | |
The following will cover information that pertains primarily with the main pump system and components that are controlled by the machine ECM.
When using this manual for the troubleshooting of the electrical system circuits, the complete electrical system schematic for your machine should also be used. Quick reference electrical connection diagrams are included throughout this manual. However, these diagrams do not show the machine wiring harness connections that are part of the circuit. The complete electrical system schematic illustrate all machine wiring harness connectors and the locations on the machine.
Electronic Control Module (ECM)
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| Illustration 2 | g03701860 |
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Electronic control modules are located to left rear side of the machine (1) Machine ECM (2) Implement 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.
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| Illustration 3 | g03701879 |
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Machine ECM connectors (1) J1 connector (2) J2 connector | |
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| Illustration 4 | g03701995 |
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Machine ECM connector (70-pin) | |
| Machine ECM - J1 Contact Connections | ||
|---|---|---|
| Pin Location | Function | Description |
| 44 | 8 VDC sensor supply | Voltage input |
| 45 | 8 VDC sensor return | Return (ECM ground) |
| 50 | Proportional output return | Return (ECM ground) |
| 52 | Main pump torque limit solenoid | Proportional output |
| 58 | Main pump displacement solenoid | Proportional output |
| 60 | Proportional output return | Return (ECM ground) |
| Machine ECM - J2 Contact Connections | ||
|---|---|---|
| Pin Location | Function | Description |
| 15 | Main pump pressure sensor | PWM input |
| 16 | Load sense pressure sensor | PWM input |
| 43 | Pilot supply pressure sensor | PWM input |
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.
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:
- Pulse Width Modulated (PWM) sensor input circuits
- Active analog (voltage) input signal circuits
- Passive analog (resistance) input signal circuits
Pulse Width Modulated (PWM) Position Sensor Operation
When 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 thumb wheel 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: Automatic calibration can be activated using Cat ET.
The main pump system contains the following sensors:
- Load sense pressure sensor
- Main pump pressure sensor
- Pilot system pressure sensor
The ECM responds to inputs by sending electrical signals to the outputs. The outputs can create an action or the outputs can provide information to the operator or service technician.
Proportional Reducing Solenoid Valve
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| Illustration 5 | g02703776 |
Note: The values in Table 3 are for bench testing only. Values may not represent parameters for machine systems specifications.
| Current Range | 0 mA ~ 700 mA |
| Coil Resistance | 11.5 ± 0.5Ω (T=20° C) |
The main pump system contains the following proportional reducing solenoids:
- Main pump limit (power shift pressure solenoid)
- Main pump displacement solenoid