| |
| Illustration 1 | g01309473 |
The decisions of the ECM are based on input data information and programming parameters. The programming parameters 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 Caterpillar® 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 used. The 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 pull the circuit high. The high voltage is detected by the ECM pull up voltage circuit. 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 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 switch input circuits
- Active analog (voltage) input signal circuits
- Passive analog (resistance) input signal circuits
To aid in diagnostics of electrical circuits controlled by the ECM, an internal "pull down voltage" is connected to switch-to-battery input circuits.
During normal operation, the switch contacts that are allowing the connection to a voltage source will hold the circuit high. Circuit conditions such as loss of switch supply voltage, disconnection in the switch circuit, or an open circuit allow a pull down of circuit voltage. The pull down voltage results 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 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 Transmission ECM are listed in the tables for the 70-pin connectors.
Communication between the Transmission 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 circuits allow 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 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 ECM is 81.
Note: All diagnostic codes for the components in the machine control system are activated by the Transmission ECM (MID 81).
Note: The following tables list every possible connection for the Transmission ECM (MID 81) and the Implement ECM (MID 82). Depending on the attachments that are installed on your machine, some of the listed circuits may not be present.
| Transmission ECM ConnectorJ1 (MID 81)
Contact Descriptions(1) |
||
|---|---|---|
| Pin # | Description | Purpose |
| 1 | Key Switch | Key Switch Input |
| 2 | XMSN Output Speed Sensor 1 (+) | Differential Speed Input (+) |
| 3 | XMSN Output Speed Sensor 1 (-) | Differential Speed Input (-) |
| 4 | XMSN Output Speed Sensor 2 (+) | Differential Speed Input (+) |
| 5 | XMSN Output Speed Sensor 2 (-) | Differential Speed Input (-) |
| 8 | Engine Speed Tach Wire (+) | Differential Speed Input (+) |
| 9 | Engine Speed Tach Wire (-) | Differential Speed Input (-) |
| 10 | Cat Data Link (+) | Cat Data Link (+) |
| 11 | +5 VDC Power Supply | Sensor Power Output |
| 12 | Parking Brake Solenoid | Sourcing Driver Output |
| 13 | (-) Unswitched Battery | Battery Return |
| 15 | XMSN Input Speed Sensor (+) | Differential Speed Input (+) |
| 16 | XMSN Input Speed Sensor (-) | Differential Speed Input (-) |
| 20 | Cat Data Link (-) | Cat Data Link (-) |
| 21 | (-) 5 VDC Sensor Return | Sensor Power Return |
| 22 | Auto Lube Grease Level Sensor | Analog Input |
| 23 | (-) Unswitched Battery | Battery Return |
| 26 | ECM Location Code 1 (Open) | ECM Location Code (Open) |
| 27 | ECM Location Code 1 (Grounded) | ECM Location Code (Ground) |
| 28 | ECM Location Code 4 (Open) | ECM Location Code (Open) |
| 29 | XMSN Oil Temperature Sensor | Analog Input |
| 30 | Torque Converter Oil Temperature Sensor | Analog Input |
| 31 | (+) Unswitched Battery | Battery Power Input |
| 32 | ECM Location Code Enable | ECM Location Code |
| 33 | Steering/XMSN Lock (N/C) | Switch to Ground Input |
| 34 | Steering/XMSN Lock (N/O) | Switch to Ground Input |
| 36 | Auto Lube Pump Pressure Sensor | Analog Input |
| 37 | Auto Lube “NEEf” Pressure Sensor | Analog Input |
| 38 | (+) Unswitched Battery | Battery Power Input |
| 39 | (+) Unswitched Battery | Battery Power Input |
| 40 | Upshift Switch (N/C) | Switch to Ground Input |
| 41 | Upshift Switch (N/O) | Switch to Ground Input |
| 42 | Downshift Switch (N/C) | Switch to Ground Input |
| 43 | Downshift Switch (N/O) | Switch to Ground Input |
| 44 | (+) 8 VDC Supply | Sensor Power Output |
| 45 | (-) 8 VDC Return | Sensor Power Return |
| 49 | Clutch 4 (Speed #2) | Sourcing Driver Output |
| 50 | PWM Return (1-4) | Sourcing Driver Return |
| 51 | Clutch 5 (Speed #1) | Sourcing Driver Output |
| 52 | Auto Lube Solenoid | Sourcing Driver Output |
| 55 | PWM Driver Return (9-12) | Sourcing Driver Return |
| 57 | (-) Unswitched Battery | Battery Return |
| 58 | Lockup Clutch Solenoid | Sourcing Driver Output |
| 59 | Impeller Clutch Solenoid | Sourcing Driver Output |
| 60 | PWM Driver Return 5-8 | Sourcing Driver Return |
| 62 | Clutch 2 (Forward) | Sourcing Driver Output |
| 63 | Autolube Grease Low Level Switch | Switch to Ground Input |
| 64 | XMSN Filter Bypass Switch | Switch to Ground Input |
| 65 | Clutch 1 (Reverse) | Sourcing Driver Output |
| 66 | Clutch 3 (Speed #3) | Sourcing Driver Output |
| 70 | (-) Unswitched Battery | Battery Return |
| (1) | Contacts that are not listed are not used. |
| Transmission ECM ConnectorJ2 (MID 81)
Contact Descriptions(1) |
||
|---|---|---|
| Pin # | Description | Purpose |
| 1 | Key Switch Start | Key Switch Input |
| 2 | Axle Oil Cooler Solenoid | Sourcing Driver Output |
| 3 | Main Relay | Sourcing Driver Output |
| 4 | Solenoid Return | Sourcing Driver Return |
| 6 | Machine Power Distribution Relay | Sourcing Driver Output |
| 7 | Start Relay | Sourcing Driver Output |
| 8 | Solenoid Return | Sourcing Driver Return |
| 9 | Powered Access Disable Relay | Sourcing Driver Output |
| 10 | Heated Mirrors Relay | Sourcing Driver Output |
| 11 | Machine Feature Alarm | Sourcing Driver Output |
| 12 | Autolube Manual Lube | Sinking Driver Output |
| 13 | Bumper XMSN Lockout LED | Sourcing Driver Output |
| 17 | Impeller Clutch Pressure Sensor | PWM Input |
| 19 | Backlight Dimmer | Sourcing Driver Output |
| 20 | Backup Alarm Relay | Sourcing Driver Output |
| 23 | Direction Switch (Neutral) | PWM Input |
| 26 | Front Axle Oil Temperature Sensor | PWM Input |
| 27 | Rear Axle Oil Temperature Sensor | PWM Input |
| 28 | Direction Switch (Reverse) | PWM Input |
| 29 | Front Brake Accumulator Pressure Sensor | PWM Input |
| 31 | Powered Access Position Switch (N/O) | Switch to Ground Input |
| 34 | Brake Charge Pressure Sensor | PWM Input |
| 35 | Torque Converter Pedal Position Sensor | PWM Input |
| 37 | Park Brake Operator Switch (N/O) | Switch To Power Input |
| 38 | Park Brake Operator Switch (N/O 1) | Switch To Power Input |
| 39 | Park Brake Operator Switch (N/O 2) | Switch To Power Input |
| 41 | Park Brake Oil Pressure | PWM Input |
| 42 | Front Service Brake Pressure | PWM Input |
| 43 | Rear Service Brake Pressure | PWM Input |
| 44 | Bumper XMSN Lockout Switch (N/C) | Switch to Ground Input |
| 45 | Autolube Pressure Fault Switch | Switch to Ground Input |
| 47 | Bumper XMSN Lockout Switch (N/O) | Switch to Ground Input |
| 49 | Direction Switch (Forward) | PWM Input |
| 50 | Fuel Level Sender | PWM Input |
| 54 | LH Armrest Switch (N/O) | Switch to Ground Input |
| 55 | LH Armrest Switch (N/C) | Switch to Ground Input |
| 56 | CAN A High | CAN Data Link (+) |
| 58 | XMSN Oil Low Level Switch | Analog Input |
| 59 | Powered Access Position Switch (N/C) | Switch to Ground Input |
| 61 | Operator Seat Belt Switch (N/O) | Switch to Ground Input |
| 62 | Operator Seat Belt Switch (N/C) | Switch to Ground Input |
| 64 | CAN B High | CAN Data Link (+) |
| 65 | CAN B Low | CAN Data Link (-) |
| 67 | CAN A High | CAN Data Link (+) |
| 68 | CAN A Low | CAN Data Link (-) |
| 70 | CAN A Low | CAN Data Link (-) |
| (1) | Contacts that are not listed are not used. |
| Implement ECM ConnectorJ1 (MID 82)
Contact Descriptions(1) |
||
|---|---|---|
| Pin # | Description | Purpose |
| 1 | Key Switch | Key Switch Input |
| 10 | Cat Data Link (+) | Cat Data Link (+) |
| 11 | (+) 5 VDC Supply | Sensor Power Output |
| 12 | Implement Pilot Supply Solenoid | Sourcing Driver Output |
| 13 | (-) Unswitched Battery | Battery Return |
| 20 | Cat Data Link (-) | Cat Data Link (-) |
| 21 | (-) 5 VDC Sensor Return | Sensor Power Return |
| 22 | Hydraulic Oil Temperature | Analog Input |
| 23 | (-) Unswitched Battery | Battery Return |
| 28 | ECM Location Code 4 (Grounded) | Switch to Ground Input |
| 29 | Cab Air Temperature Sensor | Analog Input |
| 30 | HVAC Evaporator Coil Temp Sensor | Resistive Sender (GND) |
| 31 | (+) Unswitched Battery | Battery Power Input |
| 32 | ECM Location Code Enable | Switch to Ground Input |
| 33 | Implement Lockout Switch (N/O) | Switch to Ground Input |
| 34 | Implement Lockout Switch (N/C) | Switch to Ground Input |
| 35 | Implement Pilot Oil Filter Bypass Switch | Switch to Ground Input |
| 36 | Operator Requested Cab Air Temp | Resistive Sender (GND) |
| 37 | HVAC Blower Speed Control Position | Switch to Ground Input |
| 38 | (+) Unswitched Battery | Battery Power Input |
| 39 | (+) Unswitched Battery | Battery Power Input |
| 40 | Steering/Brake Pump Case Drain Switch | Switch to Ground Input |
| 41 | Joystick Trigger Switch (N/O) | Switch to Ground Input |
| 42 | Joystick Trigger Switch (N/C) | Switch to Ground Input |
| 43 | Steering Pilot Filter Bypass Switch | Switch to Ground Input |
| 44 | (+) 8 VDC Supply | Sensor Power Output |
| 45 | (-) 8 VDC Return | Sensor Power Return |
| 48 | Raise Solenoid | Sourcing Driver Output |
| 49 | Lower Solenoid | Sourcing Driver Output |
| 50 | Solenoid Return | Sourcing Driver Return |
| 51 | Tilt Left Tip Back Solenoid | Sourcing Driver Output |
| 52 | Tilt Right Tip Forward Solenoid | Sourcing Driver Output |
| 53 | Cab Ventilation Duct Air Temperature | Resistive Sender (GND) |
| 54 | PWM Driver Return 11-12 | Sourcing Driver Return |
| 55 | Solenoid Return | Sourcing Driver Return |
| 56 | PHS 10 VDC Power Return | Sensor Power Return |
| 57 | (-) Unswitched Battery | Battery Return |
| 60 | Solenoid Return | Sourcing Driver Return |
| 69 | (+) 10 VDC Power Supply | Sensor Power Output |
| 70 | (-) Unswitched Battery | Battery Return |
| (1) | Contacts that are not listed are not used. |
| Implement ECM ConnectorJ2 (MID 82)
Contact Descriptions(1) |
||
|---|---|---|
| Pin # | Description | Purpose |
| 1 | (+) Battery For Ride Control Balance Solenoid Driver | Sensor Power Output |
| 3 | HVAC Compressor Clutch Solenoid | Sourcing Driver Output |
| 4 | 2A ON/OFF Return 1-3 | Switch Return |
| 5 | Dual Tilt (Blade Tip Solenoid) | Sourcing Driver Output |
| 6 | Dual Tilt (Blade Single Tilt Solenoid) | Sourcing Driver Output |
| 8 | ON/OFF Return | Switch Return |
| 9 | Operator Horn Relay | Sourcing Driver Output |
| 19 | HVAC Blower Motor Command | Sourcing Driver Output |
| 21 | HVAC Air Heater Engine Coolant Actuator | Sourcing Driver Output |
| 24 | Joystick Forward Reverse Axis Sensor | PWM Input |
| 25 | Joystick Left Right Axis Sensor | PWM Input |
| 26 | Joystick Thumb Rocker | PWM Input |
| 28 | Steering Coolant Oil Filter Bypass Switch | Switch to Ground Input |
| 29 | Joystick Pushbutton #1 (N/O) | Switch to Ground Input |
| 30 | Joystick Pushbutton #1 (N/C) | Switch to Ground Input |
| 36 | Steering Tank Oil Low Level Switch | Switch to Ground Input |
| 37 | Implement Tank Oil Low Level Switch | Switch to Ground Input |
| 38 | Primary Steering Pressure Switch | Switch to Ground Input |
| 39 | Joystick Pushbutton #2 (N/O) | Switch to Ground Input |
| 43 | Implement Pilot Pressure Sensor | PWM Input |
| 44 | Windshield Wiper Fluid Add Switch | Switch to Ground Input |
| 45 | Joystick Pushbutton #2 (N/C) | Switch to Ground Input |
| 48 | Demand Fan Pressure Sensor | PWM Input |
| 51 | Tilt Hydraulic Pump Pressure | PWM Input |
| 52 | Steering Tank Oil Full Level Switch | Switch to Ground Input |
| 53 | Implement Tank Oil Full Level Switch | Switch to Ground Input |
| 54 | Implement Case Drain Filter Bypass Switch | Switch to Ground Input |
| 56 | CAN A High | CAN Data Link (+) |
| 58 | Fan Return Filter Bypass Switch | Switch to Ground Input |
| 59 | Fan Motor Pump Case Drain Filter Switch | Switch to Ground Input |
| 60 | HVAC Switch (ON) | Switch to Power |
| 61 | HVAC Switch (AUTO) | Switch to Power |
| 62 | AC Refrigerant Monitoring Switch | Switch to Ground Input |
| 64 | CAN B High | CAN Data Link (+) |
| 65 | CAN B Low | CAN Data Link (-) |
| 67 | CAN A High | CAN Data Link (+) |
| 68 | CAN A Low | CAN Data Link (-) |
| 70 | CAN A Low | CAN Data Link (-) |
| (1) | Contacts that are not listed are not used. |