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| Illustration 1 | g01309473 |
The decisions made by the ECM are based on input data information and programming parameters. The programming parameters are flashed to the memory of the ECM . After the ECM receives the input information, the ECM determines the correct response and sends an output signal to the appropriate device. The internal input and output circuits of the ECM are connected to the machine wiring harness by two 70 contact connectors (J1 and J2).
Note: The ECM is not serviceable. If the ECM is damaged, the ECM must be replaced. The failure rate for the ECM is low. If the ECM failure is suspected, contact the Technical Communicator at a local dealership for possible consultation with AVSpare® before replacing the ECM. Replace the ECM only after all of the other possible causes of a particular problem have been investigated.
To aid in diagnostics of certain types of electrical circuits 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 resistor.
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 allows the circuit to be pulled high by the ECM pull up voltage. The pull up voltage will result in an above normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 3 (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 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. The pull down voltage 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.
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 needed to control machine operations. The output is 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 Transmission/Chassis ECM is listed in the tables for the 70-pin connectors.
The ECM sends electrical signals through the outputs. The outputs can create an action or the outputs can provide information to the ECM. The ECM can send output signals to the system components in one of several different electrical signal types such as: driver outputs, sinking driver outputs, sensor power supply outputs and data link outputs. The possible outputs for the ECM are listed in the tables for the 70-pin connectors.
Communication between the 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 ECM supports two types of data link systems.
- Cat Data Link
- SAE J1939 Data Link
The two types of data links are the main structure for communication between all of the control modules on the machine. More than one CAN data link system can be present on a machine. Dedicated CAN data link circuits can be used for communication between specific controls on the machine.
Communication between the Transmission/Chassis ECM and the other control modules on the machine are conducted over the J1939 Data Link circuit. The data link is connected to each control module. The ECM modules use the Cat ® Data Link to send and receive information from the Cat Electronic Technician (ET) Service Tool.
A module identifier (MID) is assigned to each ECM on a machine. The MID for the Transmission/Chassis ECM is 27. The MID for the Implement ECM is 82.
Note: The following tables list every possible connection for the ECM for the series Series 620. Depending on the attachments that are installed on your machine, some of the listed circuits may not be present.
| Transmission/Chassis ECM ConnectorJ1 (MID 27)
Contact Descriptions(1) |
|
|---|---|
| No. | Function |
| 1 | Key Switch (ON) |
| 2 | Engine Speed Sensor + |
| 3 | Engine Speed Sensor - |
| 6 | Intermediate Speed Sensor + |
| 7 | Intermediate Speed Sensor - |
| 8 | Torque Converter Output Speed Sensor + |
| 9 | Torque Converter Output Speed Sensor - |
| 10 | Cat® Data Link + |
| 11 | +5 V Sensor Supply |
| 12 | Access Ladder Down |
| 13 | - Battery |
| 14 | Keyswitch (ON) |
| 15 | Transmission Output Speed Sensor 1 + |
| 16 | Transmission Output Speed Sensor 1 - |
| 17 | Transmission Output Speed Sensor 2 + |
| 18 | Transmission Output Speed Sensor 2 - |
| 20 | Cat® Data Link - |
| 21 | +5 V Sensor Return |
| 22 | Torque Converter Oil Temperature Sensor |
| 23 | - Battery |
| 25 | CAN Keypad Wake Up |
| 26 | ECM Location 0 |
| 30 | Transmission Oil Temperature Sensor |
| 31 | +24 V Battery |
| 32 | ECM Location Enable |
| 34 | Access Ladder Position Switch (Raise) (N/O) |
| 35 | Access Ladder Position Switch (Lower) (N/C) |
| 36 | Fuel Level Sender |
| 37 | Service Brake Pressure Sensor 1 |
| 38 | +24 V Battery |
| 39 | +24 V Battery |
| 41 | Top Drive Gear Select Switch |
| 44 | 8 V Sensor Supply |
| 45 | 8 V Sensor Return |
| 47 | +24 V Battery |
| 48 | Transmission Solenoid 1 |
| 49 | Brake Charge Solenoid |
| 50 | Prop Driver 1-4 Solenoid Return |
| 51 | Transmission Solenoid 5 |
| 52 | Transmission Solenoid 7 |
| 54 | Electronic Main Relief Valve Return |
| 55 | Prop Driver 9-12 Solenoid Return |
| 56 | 10V Sensor Return |
| 57 | - Battery |
| 58 | Transmission Solenoid 2 |
| 59 | Transmission Solenoid 3 |
| 60 | Prop Driver 5-8 Solenoid Return |
| 61 | Transmission Solenoid 4 |
| 62 | Transmission Solenoid 6 |
| 64 | Transmission Charge Filter Bypass Switch |
| 65 | Differential Lock Solenoid |
| 66 | Park Brake Solenoid |
| 67 | Electronic Main Relief Valve |
| 69 | +10V Sensor Supply |
| (1) | Contacts that are not listed are not used. |
| Transmission/Chassis ECM Connector J2 (MID 27)
Contact Descriptions(1) |
|
|---|---|
| No. | Function |
| 1 | Key Switch (Crank) |
| 2 | Main Power Relay |
| 3 | Access Ladder Up |
| 4 | On/Off Driver Return (1-3) Solenoid Return |
| 6 | Secondary Steering Relay |
| 7 | Start Relay |
| 8 | ON/OFF Driver 4-6 Solenoid Return |
| 9 | Front Work Lamp Relay |
| 10 | Front Lamps Relay |
| 11 | Park/Tail/Backlight Relay |
| 12 | Hazard Lamp Relay |
| 13 | Rear Work Lamps Relay |
| 15 | Brake Accumulator Oil Pressure Sensor 2 |
| 16 | Park Brake Pressure Sensor |
| 17 | TRAC/S Brake Oil Temperature Sensor |
| 19 | Ladder Light Relay |
| 20 | Adjustable Backlighting |
| 21 | Back Up Alarm Relay |
| 22 | Switch-to-Ground Switch Return |
| 23 | Park Brake Switch (N/O)-Disengage |
| 28 | Park Brake Switch (N/C) Disengage 1 |
| 29 | Park Brake Switch (N/C) Disengage 2 |
| 30 | Operator Seat Belt Switch (N/O) |
| 31 | Operator Seat Belt Switch (N/C) |
| 32 | LH Wheel Speed Sensor |
| 33 | RH Wheel Speed Sensor |
| 35 | Transmission Shift Lever Sensor |
| 36 | Secondary Steering Test Switch |
| 37 | Engine Retarder Lever (High) |
| 38 | Engine Retarder Lever (Med) |
| 39 | Engine Retarder Lever (Low, Med, & High) |
| 41 | Primary Steering Pressure Sensor |
| 42 | Secondary Steering Pressure Sensor |
| 44 | Service Brake Pedal Switch |
| 46 | Brake Charge Pump Filter Bypass Switch |
| 47 | Fan Return Filter Bypass Switch |
| 52 | Differential Lock Switch |
| 56 | Main Machine CAN Data Link + |
| 58 | Transmission Hold Switch (N/O) |
| 59 | Transmission Hold Switch (N/C) |
| 63 | Passive Analog Sensor Return |
| 64 | CAN (B) Data Link + (Switch Pads) |
| 65 | CAN (B) Data Link - (Switch Pads) |
| 67 | Main Machine CAN Data Link + |
| 68 | Main Machine CAN Data Link - |
| 70 | Main Machine CAN Data Link - |
| (1) | Contacts that are not listed are not used. |
| Implement ECM Connector J1 (MID 82)
Contact Descriptions(1) |
|
| 1 | Key Switch |
| 10 | Cat Data Link + |
| 12 | Pilot Solenoid |
| 13 | Battery - |
| 14 | AC Manual |
| 20 | Cat Data Link - |
| 22 | Hydraulic Oil Temperature |
| 23 | Battery - |
| 24 | AC Refrigerant Circuit |
| 25 | AC Auto |
| 27 | ECM Location 1 (GND) |
| 29 | HVAC Outlet Temperature |
| 30 | Evaporator Freeze PROPN Temperature |
| 31 | Battery + |
| 32 | ECM Location Enable (GND) |
| 37 | AC Operator Temperature Control |
| 38 | Battery + |
| 44 | 8V Sensor Supply |
| 45 | 8V Sensor Return |
| 46 | Battery + |
| 50 | PROPN Driver Return 1-4 |
| 53 | AC Cab Temperature |
| 54 | PROPN Driver Return 11-12 |
| 55 | PROPN Driver Return 9-10 |
| 56 | 10V Sensor Return |
| 57 | Battery - |
| 60 | PROPN Driver Return 5-8 |
| 63 | Cushion Hitch Switch (N/O) |
| 64 | Cushion Hitch Switch (N/C) |
| 65 | Cushion Hitch Leveling Solenoid |
| 66 | Cushion Hitch Enable Solenoid |
| 69 | 10V Sensor Supply |
| 70 | Active Analog Sensor Return |
| (1) | Contacts that are not listed are not used. |
| Implement ECM Connector J2 (MID 82)
Contact Descriptions(1) |
|
| 1 | Front Washer Switch |
| 3 | Cutting Edge Camera Trigger |
| 4 | ON/OFF Driver Return 1-3 |
| 5 | RH Camera Trigger |
| 6 | RR Camera Trigger |
| 7 | Front Wiper Relay |
| 8 | ON/OFF Driver Return 4-6 |
| 10 | Rear Wiper Park Disable Relay |
| 12 | Rear Wiper Relay (High) |
| 13 | Rear Washer Relay |
| 16 | Cushion Hitch PSC |
| 19 | Compressor Clutch Relay |
| 20 | Condenser Relay |
| 21 | Water Valve Actuator |
| 22 | Switch-To-Ground Switch Return |
| 30 | Implement Lockout Switch (N/O) |
| 31 | Implement Lockout Switch (N/C) |
| 50 | Calibration Pressure Sensor |
| 56 | Main Machine CAN Data Link + |
| 59 | Cushion Hitch to Implement Pilot Pressure Filter Bypass Switch |
| 63 | Passive Analog Sensor Return |
| 67 | Main Machine CAN Data Link + |
| 68 | Main Machine CAN Data Link - |
| 70 | Main Machine CAN Data Link - |
| (1) | Contacts that are not listed are not used. |