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| Illustration 1 | g03307257 |
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| Illustration 2 | g01309473 |
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ECM Connectors and Contacts | |
The Machine ECM determines actions that are based on input information and memory information. After the Machine ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the Machine ECM are connected to the machine harness by two 70 contact connectors (J1 and J2). The ECM sends the information to the AVSpare 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.
| Machine ECM Contact Description J1 Contact Descriptions(1) | ||
|---|---|---|
| No.(2) | Type | Function |
| 6 | Differential Speed Input (+) | Engine Speed Sensor + |
| 7 | Differential Speed Input (-) | Engine Speed Sensor - |
| 11 | Sensor Power Output | 5V Sensor Supply |
| 13 | Battery Return | Battery - |
| 21 | Sensor Power Return | 5V Sensor Return |
| 23 | Battery Return | Battery - |
| 29 | Analog Input | Power Train Oil Tank Temperature Sensor |
| 30 | Analog Input | Separate Circuit Coolant Temperature Sensor |
| 31 | Battery Power Input | Battery + |
| 35 | Switch to Ground Input | Parking Brake Switch (N/O) |
| 37 | Analog Input | Power Train Lubrication Pressure Sensor |
| 38 | Battery Power Input | Battery + |
| 39 | Battery Power Input | Battery + |
| 40 | Switch to Ground Input | Parking Brake Switch (N/C) |
| 44 | Sensor Power Output | 8 V Sensor Supply |
| 45 | Sensor Power Return | 8 V Sensor Return |
| 47 | Battery Power Input | Battery + |
| 55 | Souring Driver Return | Proportional Brake Solenoid Return |
| 56 | Sensor Power Return | 10V Return |
| 57 | Battery Return | Battery - |
| 58 | Sourcing Driver Output | Proportional Brake Solenoid |
| 60 | Sourcing Driver Return | PWM Driver 5-8 Return |
| 65 | Sourcing Driver Output | Proportional Brake Valve Solenoid |
| 66 | Sourcing Driver Output | Transmission Forward Clutch |
| 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 ECM Contact Description J2(1) | ||
|---|---|---|
| No.(2) | Type | Function |
| 3 | Sourcing Driver Output | Brake Dump Valve Solenoid |
| 4 | Sourcing Driver Return | Brake Dump Valve Solenoid |
| 6 | Sourcing Driver Output | Backup Alarm |
| 8 | Sourcing Driver Return | Load Return 2 |
| 22 | Return | Sensor / Driver Return |
| 33 | PWM Input | Throttle |
| 38 | Switch To Ground Input | Speed Set/Recall (N/O) |
| 39 | Switch To Ground Input | Speed Set/Recall (N/C) |
| 42 | PWM Input | Thumbwheel PWM Shift |
| 43 | PWM Input | Travel Control Pedal Sensor |
| 48 | PWM Input | FNR 1 |
| 49 | PWM Input | FNR 2 |
| 51 | PWM Input | Bi-Directional Shift |
| 58 | Analog Input | Separate Circuit Coolant Pressure Sensor |
| 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 of 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 in order 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 3 | g03718385 |
The ECM receives signals from the engine speed sensor as a frequency signal. The engine speed sensor is a passive sensor. The signal indicates the rotational speed of the engine. The signal is generated by a gear passing in front of the sensor, with one full pulse generated per tooth on the gear. The signal is low when a gear tooth is in front of the sensor and high when in a valley.
Power Train Tank Oil Temperature Sensor
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| Illustration 4 | g03345886 |
The ECM receives signals from the power train tank oil temperature sensor as an analog signal. The sensor is a passive sensor. The voltage output of the sensor changes proportionally to the temperature of the torque converter oil.
Separate Circuit Cooling System Coolant Temperature Sensor
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| Illustration 5 | g03372390 |
The ECM receives signals from the separate circuit cooling system coolant temperature sensor as an analog signal. The sensor is a passive sensor. The voltage output of the sensor changes proportionally to the temperature of the coolant.
Separate Circuit Coolant Pressure Sensor
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| Illustration 6 | g03718548 |
The separate circuit coolant pressure sensor is an active analog sensor. The voltage of the signal varies proportionally to the pressure of the coolant. The ECM receives the signal and interprets the voltage level to determine the pressure of the coolant.
Power Train Lube Pressure Sensor
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| Illustration 7 | g03718616 |
The power train lube pressure sensor is an active analog sensor. The voltage of the signal varies proportionally to the pressure of the lubrication. The ECM receives the signal and interprets the voltage level to determine the pressure of the lubrication.
Throttle and Bi-Direction Control
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| Illustration 8 | g03719124 |
The throttle and bi-direction control selectors are active pulse width modulated sensors. The duty cycle of the signal varies based on the position of the selectors. Use the table below to determine duty cycle and position relationship.
| Switch Position | Throttle Duty Cycle | Bi Direction Duty Cycle |
| 1 | 10% | N/A |
| 2 | 23% | 23% |
| 3 | 36% | 36% |
| 4 | 49% | 49% |
| 5 | 62% | 62% |
| 6 | 75% | 75% |
| 7 | 88% | N/A |
Travel Control Pedal Position Sensor
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| Illustration 9 | g03373852 |
The travel control pedal position sensor is an active pulse width position sensor. The sensor sends a pulse width modulated signal to the ECM. The signal allows the ECM to determine the operator input request for ground speed reduction based on the position of the pedal.
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| Illustration 10 | g03373957 |
The thumbwheel sensor is an active pulse width modulated sensor. The sensor sends a pulse width modulated signal to the ECM. The duty cycle of the signal is proportional to the position of the thumbwheel. The signal allows the ECM to determine the operator input request for ground speed.
Forward Neutral Reverse Selector
The forward neutral reverse (FNR) selector generates two PWM signals. Based on the duty cycle of the two signals, the ECM determines the operator request for forward, reverse, or neutral.
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.
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| Illustration 11 | g03372717 |
The parking brake switch is a two position switch with a normally open contact and a normally closed contact. The contacts provide switch to ground inputs to the ECM. Through these contacts, the ECM can determine if the operator has engaged or disengaged the parking brake switch. The parking brake switch directly controls the action of the parking brake system, by either opening or closing the driver side circuit on the brake solenoid.
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| Illustration 12 | g03373911 |
The speed set/recall switch is a momentary switch with a normally open contact and a normally closed contact. The contacts provide switch to ground inputs to the ECM. Through these contacts, the ECM can determine if the switch is depressed or not. The ECM then uses internal programming to control the speed set/recall feature based on the operation of the switch.
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 13 | g03372925 |
The brake solenoid is designed to control the flow of brake oil to the brakes. The brakes are spring applied and hydraulically released. When the solenoid is not engaged or receiving a low duty cycle signal, the solenoid does not allow brake oil to disengage the brakes. As the duty cycle of the signal to the solenoid increases, the solenoid allows some flow and the brakes begin to release. When the duty cycle of the signal to the solenoid is at the maximum, the flow of brake oil fully releases the brakes. The engagement of the brakes is inversely proportional to the duty cycle of the signal sent by the ECM.
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.
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| Illustration 14 | g03423744 |
The brake dump solenoid is an on/off solenoid valve. The solenoid is activated when the limit switch on the brake pedal is activated. The solenoid controls if the brake hydraulic oil is being directed to the tank, or allowed to be distributed by the brake solenoid.
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| Illustration 15 | g03350044 |
The backup alarm is controlled by the power train ECM. When in the REVERSE position, the backup alarm sounds. The alarm is driven by the ECM.
Electronic communication between the Implement ECM, Machine 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 of the ECMs on the machine, and is used primarily for information and service purposes, such as the AVSpare Electronic Technician (AVS ET). The other data link systems are high speed data links used for machine control purposes.