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| Illustration 1 | g03307257 |
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(1) Chassis ECM
(2) J1 machine harness connector (3) J2 machine harness connector | |
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| Illustration 2 | g01309473 |
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ECM Connectors and Contacts | |
The Chassis ECM determines actions that are based on input information and memory information. After the Chassis ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the Chassis 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.
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 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
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.
| Chassis ECM Contact Description J1 (MID 057) Contact Descriptions(1) | ||
|---|---|---|
| No.(2) | Type | Function |
| 10 | Cat Data Link + | Cat Data Link + |
| 20 | Cat Data Link - | Cat Data Link - |
| 21 | Sensor Power Return | 5V Sensor Return |
| 26 | Switch to Ground Input | ECM Location 0 |
| 32 | Switch to Ground Input | ECM Location Enable |
| 39 | Battery Power Input | Battery + |
| 44 | Sensor Power Output | 8 V Sensor Supply |
| 45 | Sensor Power Return | 8 V Sensor Return |
| 46 | Battery Power Input | Battery + |
| 47 | Battery Power Input | Battery + |
| 50 | Souring Driver Return | PWM Drivers 1 - 4 Return |
| 54 | Souring Driver Return | PWM Driver 11-12 Return |
| 55 | Souring Driver Return | PWM Driver 9-12 Return |
| 56 | Sensor Power Return | Battery - |
| 57 | Battery Return | Battery - |
| 60 | Sourcing Driver Return | PWM Driver 5-8 Return |
| 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. |
| Chassis ECM Contact Description J2(1) | ||
|---|---|---|
| No.(2) | Type | Function |
| 3 | Sourcing Driver Output | Autolube Solenoid |
| 4 | Sourcing Driver Return | Load Return 1 |
| 8 | Sourcing Driver Return | Load Return 2 |
| 22 | Return | Sensor / Driver Return |
| 34 | PWM Input | Proportional Solenoid Return Feedback 3 |
| 40 | PWM Input | Proportional Solenoid Return Feedback 1 |
| 41 | PWM Input | Proportional Solenoid Return Feedback 2 |
| 56 | CAN Data Link + | CAN A Data Link + |
| 63 | Return | Sensor Driver Return |
| 67 | CAN Data Link + | CAN A Data Link + |
| 68 | CAN Data Link - | CAN A Data Link - |
| 70 | 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 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 3 | g03323937 |
The autolube relay is an electric switch that is controlled by the ECM. The relay controls power to the autolube pump motor. When the ECM sends a signal to the relay, the relay activates allowing power to flow to the autolube pump.
Electronic communication between the Machine Control ECM, the Implement Control 2 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 Caterpillar 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 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 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 Caterpillar 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.