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| Illustration 1 | g03307257 |
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| Illustration 2 | g01309473 |
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ECM Connectors and Contacts | |
The Machine ECM determines actions that are based on input information and memory information. After the Machine ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the Machine ECM are connected to the machine harness by two 70 contact connectors (J1 and J2). The ECM sends the information to the AVSpare Electronic Technician (Cat ET) on the Cat Data Link.
Note: The ECM is not serviceable. The ECM must be replaced if the ECM is damaged. Replace the ECM if a failure is diagnosed.
In order to aid in diagnostics of certain types of electrical circuits that are controlled by the ECM, an internal "pull up voltage" is connected to ECM switch and sensor signal input contacts. An above normal voltage is internally connected to the ECM signal input circuit through a resistor.
During normal operation, the switch or sensor signal will hold the circuit low or at a certain signal amplitude, however, circuit conditions such as a loss of power to the component, a disconnection, or an open circuit will allow the circuit to be pulled high by the ECM pull up voltage. This condition 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 circuits that have pull up voltage present are:
- Pulse Width Modulated (PWM) sensor input circuits
- Switch to Ground Input switch input circuits
- Active analog (voltage) input signal circuits
- Passive analog (resistance) input signal circuits
In order to aid in diagnostics of electrical circuits that are controlled by the ECM, an internal "pull down voltage" is connected to ECM switch to battery type input circuits.
During normal operation, the switch contacts that are allowing the connection to a voltage source will hold the circuit high. When circuit conditions such as a loss of power to the switch supply voltage, a disconnection in the switch circuit or an open circuit will allow the circuit to be pulled low by the ECM pull down voltage. This condition will result in a below normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 04 (voltage below normal) diagnostic code for the affected circuit.
| Machine ECM Contact Description J1 Contact Descriptions(1) | ||
|---|---|---|
| No.(2) | Type | Function |
| 10 | Cat Data Link + | Cat Data Link + |
| 13 | Battery Return | Battery - |
| 20 | Cat Data Link - | Cat Data Link - |
| 23 | Battery Return | Battery - |
| 31 | Battery Power Input | Battery + |
| 38 | Battery Power Input | Battery + |
| 39 | Battery Power Input | Battery + |
| 44 | Sensor Power Output | 8V Supply |
| 45 | Sensor Power Return | 8V Return |
| 47 | Battery Power Input | Battery + |
| 54 | Sourcing Driver Return | Steering Solenoid Return |
| 56 | Sensor Power Return | 10V Return |
| 57 | Battery Return | Battery - |
| 67 | Sourcing Driver Output | Left Steering Solenoid |
| 68 | Sourcing Driver Output | Right Steering Solenoid |
| 69 | Sensor Power Output | 10V Supply |
| 70 | Battery Return | Battery - |
| (1) | Contacts that are not listed are not used. |
| (2) | The connector contacts that are not listed are not used. |
| Machine ECM Contact Description J2(1) | ||
|---|---|---|
| No.(2) | Type | Function |
| 22 | Return | Sensor / Driver Return |
| 23 | Switch to Ground Input | Steering Filter Bypass Switch |
| 24 | PWM Input | Steering Position Sensor 1 |
| 25 | PWM Input | Steering Position Sensor 2 |
| 34 | PWM Input | Steering Motor Speed Sensor 1 |
| 35 | PWM Input | Steering Motor Speed Sensor 2 |
| 67 | CAN Data Link + | CAN A Data Link + |
| 68 | CAN Data Link - | CAN A Data Link - |
| (1) | The ECM responds to an active input only when all of the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
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 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.
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| Illustration 3 | g03375681 |
The steering control handle has two active pulse width modulated position sensors inside of the base. The sensors determine the position of the steering handle. The ECM uses the pulse width modulated signals to determine operator steering requests. Based on the signals, the ECM controls the steering system.
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| Illustration 4 | g03376774 |
The steering motor speed sensor is an active frequency sensor. There are two proportional frequency signals produced by the sensor. The sensor detects the passing of a timing gear, and converts the speed of the timing gear into a frequency signal. Based on the signals the ECM receives from the sensor, the ECM can determine the speed of the steering motor.
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.
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| Illustration 5 | g03548458 |
The steering filter bypass switch is a pressure switch. The switch alerts the ECM when the steering filter is being bypassed. The contact floats to a high voltage when the switch is not closed. When the switch closes, the contact is pulled to a low or ground voltage state by the return line.
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.
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| Illustration 6 | g03375206 |
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Left steering pump solenoid Right steering pump solenoid | |
Each of these solenoid valves is designed to control the flow of oil to the steering pump. The two solenoids work opposite each other to shift a spool. The movement of the spool controls the steering pump direction and flow. The solenoids are proportional solenoids, and if the ECM sends a higher duty cycle signal to one, and a lower duty cycle signal to the other, the valve spool will shift, causing the steering pump to cause the machine to turn.
Note: The solenoid coils are not designed to operate using 24 DCV directly. The ECM sends a PWM signal of 24 V at a duty cycle that will provide the necessary current to the solenoid coils. Do NOT activate the coils by using 24 DCV (+battery). The life of the coils will be reduced drastically. A source of 12 DCV should be used, if the coils must be activated by not using the ECM.
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| Illustration 7 | g03675504 |
The implement lockout switch is an on/off type solenoid. The solenoid is activated by the ECM depending on operating conditions and operator request. When the solenoid is energized, the solenoid opens and allows hydraulic oil to flow to the implement system.
Electronic communication between the Machine Control ECM, the Engine ECM, and the other control modules on the machine is conducted over data link circuits. The data link circuits allow the sharing of information with other electronic control modules. The data link circuits are bidirectional. The data link circuit allows the ECM to send information and to receive information.
The electronic communication system consists of two types of data link systems.
- Cat Data Link
- SAE J1939 (CAN) Data Link
The two types of data links are the main structure for communication between all of the control modules on the machine.
The SAE J1939 Data Link circuit is mostly used for faster operational communication between the control modules on the machine. The Cat Data Link is used for some of the internal communication that does not require the faster speeds and is used for communication with external devices such as the AVSpare Electronic Technician (Cat ET) service tool.
The Cat Data Link is an input/output of the ECM. The data link uses the connector for the service port in order to communicate with the AVSpare Electronic Technician. A data link connection is provided for the product link.
Note: The control for the product link provides a global positioning system for the machine.
The data link is bidirectional. The bidirectional link allows the ECM to input information and output information. The data link consists of the following parts: internal ECM circuits, the related harness wiring, the service tool connector and the connector for the product link. The Cat Data Link connects to the ECM at contact J1-10 (wire 893-GN(Green)) and contact J1-20 (wire 892-BR(Brown)).
- The ECM receives commands from the Cat ET in order to change the operating modes. The Cat ET will read the service codes that are stored in the memory of the ECM. The Cat ET will clear the service codes that are stored in the memory of the ECM.
- The ECM sends the input and the output information to the AVSpare ET.
Note: An electronic control module that uses the Cat Data Link will have a module identifier. The MID for the Machine Electronic Control Module is 039.
A data link is required for communication with the service tool (Cat ET) and the electronic control modules as well as instrument clusters and other devices that use this communications protocol. The data link is not used in order to broadcast any diagnostic information.