Electronic Control Module (ECM)
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| Illustration 1 | g02612416 |
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Machine ECM (1) Controller (2) J1 Connector (3) J2 Connector | |
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| Illustration 2 | g02613001 |
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Connectors of Machine ECM (2) J1 Connector (3) J2 Connector | |
The output from the Machine ECM is based on input information from the sensors. The output commands are based on the software programmed into the control module. After the Machine ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the ECM are connected to the machine harness by two 54-pin connectors (J1 and J2). The inputs and outputs to the ECM can be viewed through the Caterpillar Electronic Technician (Cat ET). Input and output information can also be viewed using the Operator Monitor.
The ECM also communicates with sensors and other control modules via the CAN Data Link. The data link is bi-directional, allowing the Machine ECM to both receive and send information with the Engine ECM. The Machine ECM also communicates to input and output components that are directly connected to the Switch Panel. The Switch Panel is used to link input and output components to the Machine ECM via the CAN Data Link.
Note: Only the complete ECM is serviced (no lower levels components). The ECM must be replaced if the ECM is damaged. Replace the ECM if a failure is diagnosed.
The Cat Data Link is used to provide a connection for the service tool for troubleshooting, testing, and calibrations. The data link is bidirectional. The data link allows the ECM to receive information. The data link also allows the ECM to send information.
| Machine ECM Connector J1 Contact Descriptions(1) | ||
|---|---|---|
| No. | Type | Pin Description |
| 1 | Power | +Battery |
| 2 | Ground | Ground |
| 27 | Power | Power Supply for Sensor (8V) |
| 31 | Input | Implement Pressure Switch |
| 39 | Input | Travel Pressure Switch |
| 53 | Input | Drive Pump Pressure Sensor |
| 54 | Input | Idler Pump Pressure Sensor |
| (1) | Contacts that are not listed are not used. |
| Machine ECM Connector J2 Contact Descriptions(1) | ||
|---|---|---|
| No. | Type | Pin Description |
| 8 | Output | PS Pressure EPRV |
| 22 | Ground | PRV Return |
| 47 | Input/Output | CAN (J1939) Data Link + |
| 48 | Input/Output | CAN (J1939) Data Link - |
| 50 | Input/Output | Machine CAN Data Link + |
| 51 | Input/Output | Machine CAN Data Link - |
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. The controller will recognize the following types of sensor signals:
Frequency - The sensor will produce an AC signal (sine wave or square wave) that varies in frequency (Hz) as the condition changes.
Pulse Width Modulated - The sensor produces a digital signal and varies the duty cycle as the condition changes. The frequency of the signal will remain constant.
In some cases the operator is provided a manual switch that can be used to change a condition of the machine.
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| Illustration 3 | g02263513 |
Note: The values in Table 3 are for bench testing only. Values may not represent parameters for machine systems specifications.
| Operating Pressure | |
| Supply Voltage | +7V ~ +14V |
| Output Signal | 500 ± 100 Hz (PWM) |
| Output Range | 5% ~ 95% |
Drive Pump Pressure Sensor and Idler Pump Pressure Sensor
The drive pump pressure sensor and idler pump pressure sensors are inputs to the machine ECM. The drive pump and idler pump pressure sensors are located on the main control valve. The drive pump pressure sensor monitors the pressure of the drive pump oil in the front half of the main control valve high-pressure passages. The idler pump pressure sensor monitors the idler pump oil pressure in the rear half of the main control valve high-pressure passages.
The pressure sensors send a pulse width modulated (PWM) input to the machine ECM. This pressure information is used for pump control and travel speed.
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| Illustration 4 | g02332474 |
The values in Table 4 are for bench testing only. Values may not represent parameters for machine systems specifications.
| Activation Pressure | |
| Deactivation Pressure | |
| Rating | + 12V ~ +32V
0.01 Amp to 1 Amp |
| Pressure Range | 0 to 10 MPa |
The implement pressure switch sends an input signal to the machine ECM. When the joysticks are moved from the NEUTRAL position for a boom RAISE, stick IN, stick OUT, bucket IN, or a bucket OUT operation, pilot oil is directed to the implement pressure switch. The increase of pilot pressure activates the implement pressure switch. The implement pressure switch sends an electrical signal to the machine ECM. The switch information is used to control engine speed and pump control. Also, an electrical signal from the machine ECM energizes the swing brake solenoid valve in order to release the swing parking brake.
Note: The implement pressure switch does not detect a boom LOWER or a swing operation.
The travel pressure switch detects a travel operation. The travel pressure switch sends an input signal to the machine ECM. The machine ECM uses the switch information to control the engine speed and pump control.
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.
Proportional Reducing Solenoid Valve
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| Illustration 5 | g02703776 |
| Current Range | 0 mA ~ 700 mA |
| Coil Resistance | 15.0 ± 0.7 Ω (T=20° C) |
The power shift pressure PRV is used to destroke the main pump under load to maintain engine speed. The main functions of the PRV, in conjunction with, the monitoring system, are listed below:
- The PRV manages the transfer to engine power into hydraulic power as needed.
- The system control the output of the pump according to the workload, improving fuel efficiency.
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 Caterpillar 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 J2-16 (wire 892-BR(Brown)) and contact J2-25 (wire 893-GN(Green)).
- 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 Caterpillar ET.
A Controller Area Network (CAN) Data Link allows communication between the Machine ECM, Engine ECM, and the input and output devices of the switch panel. The CAN Data Link allows for bi-directional electronic signals to be passed among the controllers and the switch panel. The data link allows the Machine ECM to be connected to sensors and actuators connected to the switch panel. The Machine ECM can also use the data link to communicate engine speed and/or torque requirements to the Engine ECM.