Electronic Control Module (ECM)
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| Illustration 1 | g03032197 |
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(1) Connector view from ECM side
(2) Connector view from harness side | |
The ECM bases decisions on input information and memory information. After the 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 70 contact connectors (J1 and J2). The inputs and outputs to the ECM can be viewed through the Caterpillar Electronic Technician (Cat ET).
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.
| Transmission ECM Connector J1 Contact Descriptions(1) | ||
|---|---|---|
| No. | Type | Function |
| 1 | Key Switch Input | Key Switch (Key in ON Position) |
| 10 | CAT Data Link (+) | CAT Data Link (High) |
| 11 | Sensor Power Output | +5 Sensor Supply |
| 13 | Battery Return | Battery - |
| 20 | CAT Data Link (-) | CAT Data Link (Low) |
| 21 | Sensor Power Return | + 5V Sensor Supply Return |
| 23 | Battery Return | Battery - |
| 31 | Battery Power Input | Battery +24 V |
| 44 | Sensor Power Output | 8 V Supply |
| 45 | Sensor Power Return | 8 V Return |
| 46 | Battery Power Input | Battery +24 V |
| 47 | Battery Power Input | Battery + 24 V |
| 53 | Analog Input | Hydraulic Oil Temperature Sensor |
| 54 | Sourcing Driver Return | Hoist Raise/Lower Solenoid Return |
| 56 | Sensor Power Return | 10V Return |
| 57 | Battery Return | Battery - (Ground) |
| 67 | Sourcing Driver Output | Hoist Raise Solenoid |
| 68 | Sourcing Driver Output | Hoist Lower Solenoid |
| 69 | Sensor Power Output | 10 V Sensor Supply |
| 70 | Battery Return | Battery - |
| (1) | System-specific pin locations |
| Transmission ECM Connector J2 Contact Descriptions(1) | ||
| No. | Type | Function |
| 1 | Switch to Battery Input/Sourcing Driver Enable (J2-7 Only) | Key Start ( Key In Crank Position) |
| 15 | PWM Input | Hoist Lever Sensor |
| 30 | Switch to Ground Input | Hydraulic Tank Filter Bypass Switch |
| 40 | PWM Input | Body Up/Down Switch |
| 63 | Return | Ground |
| 67 | CAN A Data Link (+) | CAN B Data Link ( High) |
| 68 | CAN A Data Link (-) | Can B Data Link ( Low) |
| 69 | CAN Data Link (Shield) | CAN A Data Link (Shield) |
| (1) | System-specific pin locations |
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.
Hydraulic Oil Temperature Sensor
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| Illustration 2 | g02108634 |
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Hydraulic Oil Temperature Sensor | |
The temperature sensor for the hydraulic oil informs the ECM of the temperature of the hydraulic system oil.
The sensor is designed internally to change resistance based on the temperature of the hydraulic oil. The transmission ECM uses up a pull resistor to receive sensor voltage and convert the voltage to a temperature reading. The resistance range for this sensor is 33,650 ohms at
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| Illustration 3 | g03508459 |
Hoist lever sensor informs the ECM what position the hoist lever is in.
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| Illustration 4 | g03096077 |
The key switch is an input to the ECM. Power is supplied to the ECM from the key switch. Power is supplied to the ECM from the key switch when the key switch is in the START or RUN position.
The key switch is a switch to battery input and is active when the key switch is in the START or RUN position. When the key switch is turned to START, the ECM receives a + battery signal from the key switch. If all start interlocks are satisfied, the ECM will send a + battery signal to the start relay to start the engine.
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| Illustration 5 | g03511317 |
The body up/retract switch is a magnetic switch that informs the ECM if the body of the machine is up or down.
Note: The switch will also inform the ECM if the ejector blade is retracted or not for ejector machines.
Hydraulic Tank Filter Bypass Switch
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| Illustration 6 | g03015918 |
The bypass switch is a pressure switch that shows whether the filter is plugged and the filter is being bypassed. This switch is normally closed. When the filter becomes plugged, the pressure of the oil opens the switch which allows the oil to bypass the filter.
This switch is one of the inputs that is used to drive the "system indicator" in the instrument cluster. This indicator is turned ON when the "Hydraulic Tank Filter Bypass" switch is in the open position and the pilot oil temperature is greater than
The ECMs respond 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 | g03510996 |
The hoist raise solenoid controls the speed of the bed cylinders as the bed of the truck is raised (ejected for ejector models).
The hoist lower solenoid controls the speed of the bed cylinders as the bed of the truck is lowered (retracted for ejector models).
The Cat Data Link is an input/output of the ECM. The data link uses the connector for the service port 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 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 Transmission Electronic Control Module is 1B.
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.