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| Illustration 1 | g01309473 |
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ECM Connectors and Contacts | |
The Machine Control ECM determines actions that are based on input information and memory information. After the Machine Control ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the Machine Control ECM are connected to the machine harness by two 70 contact connectors (J1 and J2). The ECM sends the information to the Caterpillar 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.
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 resister.
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
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 Control ECM Contact Description J1 Contact Descriptions(1) | ||
|---|---|---|
| No.(2) | Type | Function |
| 10 | CAN C Data Link - | CAN C Data Link - |
| 13 | Battery Return | Battery - |
| 20 | CAN C Data Link + | CAN C Data Link + |
| 21 | Sensor Power Return | 5V Sensor Return |
| 23 | Battery Return | Battery - |
| 31 | Battery Power Input | Battery + |
| 36 | Analog Input | Steering Pump Charge Press Snsr |
| 38 | Battery Power Input | Battery + |
| 39 | Battery Power Input | Battery + |
| 44 | Sensor Power Output | 8 V Sensor Supply |
| 45 | Sensor Power Return | 8 V Sensor Return |
| 47 | Battery Power Input | Battery + |
| 50 | Souring Driver Return | PWM Drivers 1 - 4 Return |
| 55 | Souring Driver Return | PWM Driver 9-12 Return |
| 56 | Sensor Power Return | 10V Return |
| 57 | Battery Return | Battery - |
| 60 | Sourcing Driver Return | PWM Driver 5-8 Return |
| 67 | Sourcing Driver Output | Left Steering Clutch Solenoid |
| 68 | Sourcing Driver Output | Right Steering Clutch Solenoid |
| 69 | Sensory Power Output | 10V Sensor 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 Control 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 POS SNSR |
| 25 | PWM Input | Steering POS SNSR |
| 34 | PWM Input | Steering Motor Spd Snsr 1 |
| 35 | PWM Input | Steering Motor Spd Snsr 2 |
| 38 | Switch to Ground Input | Speed Set/Recall N.O. |
| 39 | Switch to Ground Input | Speed Set/Recall N.C. |
| 40 | PWM Input | Diff Steering Press Snsr 2 |
| 41 | PWM Input | Diff Steering Press Snsr 1 |
| 48 | PWM Input | FNR Position Snsr |
| 49 | PWM/Analog Input | Steering Posn Snsr 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 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 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 2 | g03452236 |
The steering control handle has two active pulse width modulated position sensors inside 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 3 | g06255283 |
The steering pressure sensor sends a PWM signal to the Machine ECM indicating system pressure. The duty cycle of the signal will vary in proportion to the system pressure. These PWM signals are inputs to the Machine ECM.
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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.
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| Illustration 5 | g06255283 |
The steering charge pressure sensor is an active analog sensor. The voltage output of the sensor increases proportionally to the pressure the sensor is exposed to. The ECM monitors the voltage output of the sensor to determine the pressure of the steering charge system.
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.
Steering Charge Filter Bypass Switch
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| Illustration 6 | g03348326 |
The steering charge filter bypass switch is a pressure switch. The switch alerts the ECM when the steering charge 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 7 | g06347910 |
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Left steering pump solenoid Right steering pump solenoid | |
Each of these solenoid valves is designed to control the flow of pilot oil or control 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.
Electronic communication between the Implement ECM, Machine Control ECM, 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 multiple CAN datalink systems.
The SAE J1939 CAN Data Link circuit is separated into different groups. "CAN A" is connected to all the ECMs on the machine, and is used primarily for information and service purposes, such as the Caterpillar Electronic Technician (CAT ET). The other data link systems are high-speed data links used for machine control purposes.