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| Illustration 1 | g03737020 |
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(1) Connector view from ECM side
(2) Connector view from harness side | |
Control of the power train is achieved by electronically controlled hydraulic actuation. Control of the power train is maintained by the electronic control module.
The electronic control module is also responsible for controlling the other systems that are used on the machine.
The ECM bases decisions based on input information and memory information. The ECM receives inputs from different sensors and from operator requests. The ECM sends electronic signals to control transmission shifts and other power train components.
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.
A service technician can use Caterpillar ET to communicate with the ECM. The service technician can interrogate the ECM for details of faults and the service technician can monitor operating conditions.
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.
| Power Train ECM ConnectorJ1
Contact Descriptions (1) |
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|---|---|---|
| No. | Type | Function |
| 1 | Key Switch Input | Key switch ON |
| 3 | Differential Speed Input (-) | Engine speed to transmission control |
| 4 | Differential Speed Input (-) | Transmission intermediate speed sensor 2 |
| 5 | Differential Speed Input (-) | Transmission intermediate speed sensor 1 |
| 10 | Cat Data Link (+) | Cat Data Link (+) |
| 13 | Battery Return | Battery - |
| 16 | Differential Speed Input (-) | Transmission output speed sensor 1 |
| 18 | Differential Speed Input (-) | Transmission output speed sensor 2 |
| 20 | Cat Data Link (-) | Cat Data Link (-) |
| 22 | Analog Input | Torque converter oil temperature sensor |
| 23 | Battery Return | Battery - |
| 26 | Switch to Ground Input | EMC location 0 (Ground) |
| 30 | Analog Input | Transmission oil temperature sensor |
| 31 | Battery Power Input | Battery + |
| 32 | Switch to Ground Input | ECM location enable (Ground) |
| 38 | 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 + |
| 48 | Sourcing Driver Output | Transmission solenoid 1 |
| 49 | Sourcing Driver Output | Transmission solenoid 2 |
| 50 | Sourcing Driver Return | Transmission solenoid 1&2 return |
| 51 | Sourcing Driver Output | T/C lockup clutch solenoid (All) |
| 53 | Analog Input | Hydraulic oil temperature sensor (All) |
| 54 | Sourcing Driver Return | 2 wire PROP driver return (11-12) |
| 55 | Sourcing Driver Return | Transmission solenoid 3&4 return |
| 56 | Sensor Power Return | 10V Return |
| 57 | Battery Return | Battery - |
| 58 | Sourcing Driver Output | Transmission solenoid 5 |
| 59 | Sourcing Driver Output | Transmission solenoid 6 |
| 60 | Sourcing Driver Return | Transmission 5,6, MRV, cooling fan solenoid return |
| 61 | Sourcing Driver Output | Transmission Main Relief Valve (MRV) solenoid |
| 62 | Sourcing Driver Output | Machine cooling fan solenoid |
| 65 | Sourcing Driver Output | Transmission solenoid 3 |
| 66 | Sourcing Driver Output | Transmission solenoid 4 |
| 69 | Sensor Power Output or | 10V Sensor supply |
| 70 | Battery Return | Battery - |
| (1) | Contacts that are not listed are not used. |
| Power Train ECM ConnectorJ2
Contact Descriptions (1) |
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|---|---|---|
| No. | Type | Function |
| 1 | Switch to Battery Input | Key ON |
| 29 | Switch to Ground Input | Transmission filter bypass switch |
| 30 | Switch to Ground Input | Hydraulic tank filter bypass switch |
| 46 | Switch to Ground Input | Retarder level high |
| 47 | Switch to Ground Input | Retarder level medium |
| 54 | Switch to Ground Input | Retarder level low |
| 63 | Return | Ground |
| 67 | CAN Data Link (+) | CAN A (High-J939) |
| 68 | CAN Data Link (-) | CAN A (Low-J939) |
| (1) | Contacts that are not listed are not used. |
Electronic Control Module (ECM)
The electronic control module (ECM) is at the right rear side of the cab. The ECM controls the shifting of the transmission. The transmission control sends the operator input to the ECM. The operator input indicates the desired speed for the transmission and the desired direction for the transmission. The ECM decisions are based on the input information and on the memory information. After the ECM receives the input information and the memory information, the ECM sends a corresponding response to the outputs. The inputs and the outputs are connected to the machine harness by two 70-pin connectors.
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.
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| Illustration 2 | g06198622 |
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Power train inputs and outputs (1) Transmission ECM (2) Engine ECM (3) Aftertreatment ECM (4) Chassis ECM (5) Eco Mode Status LED (6) Eject / Body UP Switch (7) Hydraulic Tank Filter Bypass Switch (8) Key Start Switch (9) Parking Brake Sensor (10) Parking brake Pressure Sensor (11) Retarder Lever (I-II-A) (Except 740GC) (12) Transmission OIl Filter Bypass Switch (13) Transmission Hold/Waiting Brake Switch (14) Front, Center, and Rear Axle Brake Temperature Sensors (15) Brake Pressure Sensor #1 (16) Brake Pressure Sensor #2 (17) Engine Speed Sensor (18) Assisted Hoist Enable Switch (19) Primary Starting Pressure Switch (20) Speed Limit Switch (21) Service Brake Pedal Switch #1 (22) Fuel Level Sender (23) Hoist Control Position Sensor (24) Hydraulic Oil Temperature Sensor (25) Secondary Steering Relay (26) Service Brake Pedal Switch #2 (27) Transmission Control Position Sensor (28) Torque Converter Temperature Sensor (29) Transmission Oil Temperature Sensor (30) Transmission Intermediate Speed Sensor #2 (31) Transmission Intermediate Speed Sensor #1 (32) Transmission Output Speed Sensor #1 (33) Transmission output Speed Sensor #2 (34) Brake Oil Filter Bypass Switch (35) Emergency Brake Switch (36) Starter Motor Relay (37) Starter Motor / Park Brake Solenoid Return (38) Demand Fan Solenoid (39) Service Brake Charge Solenoid (40) Hoist LOWER Solenoid (41) Hoist Raise Solenoid (42) Parking Brake Solenoid (43) Main Relief Valve (eMRV) Solenoid (44) T/C Lockup Clutch Solenoid (45) Transmission Solenoids (46) Backup Alarm / Lights | |
The CAT Data Link is used to communicate with the other electronic control modules on the machine. The CAT Data Link is bidirectional. The CAT Data Link allows the sharing of information with other electronic controls.
- The Power Train ECM receives the harness code input from the Caterpillar Monitoring System.
- The Power Train ECM sends the following information to the Caterpillar Monitoring System: engine speed, machine ground speed, parking brake switch status, transmission speed selection, and service code of the transmission.
- The monitoring system displays this information for the operator or for service personnel.
- The Power Train ECM communicates with the engine ECM to allow controlled throttle shifting.
The machine has several input devices. Input devices inform the ECM of the operating conditions of the machine. The machine has two types of inputs, switch inputs and sensor inputs. The switch inputs of the ECM are provided with the following signals from the switches: an open, a ground and a +battery. Sensors provide a constantly changing signal to the ECM.
The ECM responds to decisions by sending electrical signals through the outputs. The outputs can create an action or the outputs can provide information to the ECM.
Sensors provide information to the power train electronic control module (ECM) about changing conditions. The sensor signal changes proportionally to the changing conditions. The following sensor signals are recognized by the power train ECM.
- Frequency signals: The frequency (Hz) of the sensor signal varies as the condition changes.
- Pulse width modulated signals (PWM): The duty cycle of the sensor signal varies as the condition changes. The frequency of this signal is constant.
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| Illustration 3 | g00288430 |
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Pulse Width Modulated Signal | |
Speed Sensors (Engine Output, Transmission Output, and Transmission Intermediate)
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| Illustration 4 | g03799363 |
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Location of Engine Speed Sensor (1) Engine speed sensor | |
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| Illustration 5 | g03798757 |
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(2) Transmission output speed sensors
(3) Transmission Intermediate Speed Sensors (4) Wheel output speed sensors | |
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| Illustration 6 | g02783449 |
There are two transmission output speed sensors and transmission intermediate speed sensors. There are six differential output speed sensors, one on each final drive. These speed sensors are "Hall effect" type sensors. Current loop sensors generate a square wave signal from the gear teeth as the gear teeth pass the sensor. The sensor produces a signal that equals one pulse per gear tooth. This signal is sent to the transmission ECM. The transmission ECM measures the frequency of the signal to determine the speed. In the case of dual sensors, the transmission ECM receives signals from the speed sensors and the ECM uses the difference in input from the speed sensors to determine the direction of the system. The transmission ECM uses the input from the speed sensors to regulate transmission shifts. Each speed sensor has two connections to the transmission ECM (+ and −).
The transmission ECM sends the speed information to other electronic control modules via the CAT Data Link. For all the speed sensors, connector contact 2 is the signal line and connector contact 1 is the return line.
Note: The speed sensors are used to diagnose each other during normal operation. The transmission ECM periodically checks the value from the speed sensor. If an incorrect value is found, the transmission ECM will log a service code that indicates a fault for a speed sensor circuit.
For more information, refer to the following manuals:
- For transmission electronic control system, refer to Systems Operation, "Power Train Electronic Control System"
- For Data Link, refer to Systems Operation, "Data Link"
- For the transmission electronic control module (ECM), refer to Systems Operation, "Electronic Control Module (Power Train)"