Note: The ECM is not serviceable. If the ECM is damaged, the ECM must be replaced. The ECM failure is unlikely. 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 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 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 will allow 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 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
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. 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. Each 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 each 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 each ECM are listed in the tables for the 70-pin connectors.
Communication between each 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 each ECM and the other control modules on the machine are conducted over the J1939 Data Link circuit that is connected to each control module. The ECMs use the Cat Data Link to send and receive information from the Cat® Electronic Technician (Cat ET) Service Tool.
A module identifier (MID) is assigned to each ECM on a machine. The MID for the Power Train ECM is 81. The MID for the Implement ECM is 82
Note: The following tables list every possible connection for the Machine ECM. Depending on the attachments that are installed on your machine, some of the listed circuits may not be present.
| Contact Description J1(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Key Switch Run | Key Switch Input |
| 10 | Cat Data Link (+) | Cat Data Link (+) |
| 11 | 5 VDC Sensor Power | Sensor Power Output |
| 12 | Implement Pilot Supply | Sourcing Driver Output |
| 13 | - Battery (1) | Battery Return |
| 14 | Seatbelt Monitor | Switch to Battery Input |
| 20 | Cat Data Link (-) | Cat Data Link (-) |
| 21 | 5 VDC Sensor Return | Sensor Power Return |
| 22 | Operator Present | Analog Input |
| 23 | - Battery (2) | Battery Return |
| 24 | Quick Coupler Retract | Switch to Battery Input |
| 25 | Quick Coupler Extend | Switch to Battery Input |
| 26 | Identification Code 1 | Switch to Ground Input |
| 27 | Identification Code 2 | Switch to Ground Input |
| 28 | Identification Code 4 | Switch to Ground Input |
| 29 | Hydraulic Oil Temperature | Analog Input |
| 30 | Battery Cable Voltage Monitor | Analog Input |
| 31 | + Battery (1) | Battery Power Input |
| 32 | Identification Code Enable | Switch to Ground Input |
| 33 | Implement Lockout Switch (N/O) | Switch to Ground Input |
| 34 | Implement Lockout Switch (N/O) | Switch to Ground Input |
| 37 | Steering Valve Spool Position Sensor | Analog Input |
| 39 | + Battery (2) | Battery Power Input |
| 41 | Armrest Position Switch (N/C) | Switch to Ground Input |
| 42 | Armrest Position Switch (N/O) | Switch to Ground Input |
| 44 | 8V Power Supply | Sensor Power Output |
| 45 | 8V Return | Sensor Power Return |
| 47 | + Battery (3) | Battery Power Input |
| 48 | Raise Solenoid | Sourcing Driver Output |
| 49 | Lower Solenoid | Sourcing Driver Output |
| 50 | Driver Return | Sourcing Driver Return |
| 51 | Rack Solenoid | Sourcing Driver Output |
| 52 | Dump Solenoid | Sourcing Driver Output |
| 54 | Driver Return | Sourcing Driver Return |
| 55 | Driver Return | Sourcing Driver Return |
| 56 | 10 VDC Return | Sensor Power Return |
| 57 | - Battery (3) | Battery Return |
| 58 | 3rd Function Solenoid Port A | Sourcing Driver Output |
| 59 | 3rd Function Solenoid Port B | Sourcing Driver Output |
| 60 | Driver Return | Sourcing Driver Return |
| 61 | 4th Function Solenoid Port A | Sourcing Driver Output |
| 62 | 4th Function Solenoid Port B | Sourcing Driver Output |
| 64 | Hydraulic Filter Bypass Switch | Switch to Ground Input |
| 65 | EH Pump Actuator 1 | Sourcing Driver Output |
| 66 | EH Pump Actuator 2 | Sourcing Driver Output |
| 67 | Left Primary Steering Solenoid | Sourcing Driver Output |
| 68 | Right Primary Steering Solenoid | Sourcing Driver Output |
| 69 | +10 VDC Power Supply | Sensor Power Output |
| 70 | - Battery (4) | Battery Return |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
| Contact Description J2(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Battery In | Switch to Battery Input |
| 2 | Primary Steering Pilot Supply | Sourcing Driver Output |
| 3 | Force Feedback Motor Enable | Sourcing Driver Output |
| 4 | Driver Return | Sourcing Driver Return |
| 5 | Ride Control Solenoid 1 Activation | Sourcing Driver Output |
| 6 | Ride Control Solenoid 2 Balance | Sourcing Driver Output |
| 7 | Backup Alarm | Sourcing Driver Output |
| 8 | Driver Return | Sourcing Driver Return |
| 9 | Machine Feature Alarm | Sinking Driver Output |
| 15 | Left Steer Cylinder Position Sensor | PWM Input |
| 16 | Right Steer Cylinder Position Sensor | PWM Input |
| 17 | Tilt Position Sensor | PWM Input |
| 18 | Lift Position Sensor | PWM Input |
| 19 | Secondary Steering Request Output | Sinking Driver Output |
| 20 | Backlighting Control | Sinking Driver Output |
| 21 | Force Feedback Desired Torque | Sinking Driver Output |
| 23 | Store Switch | Switch to Ground Input |
| 24 | Lift Lever Position Sensor | PWM Input |
| 25 | Tilt Lever Position Sensor | PWM Input |
| 26 | Third Lever Position Sensor | PWM Input |
| 27 | Fourth Lever Position Sensor | PWM Input |
| 28 | Heated Mirror Switch | Switch to Ground Input |
| 32 | Steering Lever Position Sensor 1 | PWM Input |
| 33 | Implement Pump Discharge Pressure | PWM Input |
| 34 | Steering Lever Position Sensor 3 | PWM Input |
| 35 | Force Feedback Motor Current | PWM Input |
| 40 | EH Pump Displacement Sensor 1 | PWM Input |
| 42 | EH Load Sense Pressure | PWM Input |
| 43 | Steering Pump Oil Pressure Sensor 2 | PWM Input |
| 44 | Autodig Trigger Switch (N/O) | Switch to Ground Input |
| 45 | Autodig Trigger Switch (N/C) | Switch to Ground Input |
| 48 | Steering Lever Position Sensor 2 | PWM Input |
| 49 | Lift Cylinder HE Pressure Sensor | PWM Input |
| 50 | Lift Cylinder RE Pressure Sensor | PWM Input |
| 67 | CAN A Data Link + | CAN Data Link (+) |
| 68 | CAN A Data Link - | CAN Data Link (-) |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
| Contact Description J1(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Key Switch Run | Key Switch Input |
| 2 | XMSN Input Sp+ | Differential Speed Input (+) |
| 3 | XMSN Input Speed - | Differential Speed Input (-) |
| 4 | Planetary Member Speed + | Differential Speed Input (+) |
| 5 | Planetary Member Speed - | Differential Speed Input (-) |
| 6 | XMSN Output Speed 1+ | Differential Speed Input (+) |
| 7 | XMSN Output Speed 1- | Differential Speed Input (-) |
| 8 | XMSN Output Speed 2+ | Differential Speed Input (+) |
| 9 | XMSN Output Speed 2- | Differential Speed Input (-) |
| 10 | Cat Data Link (+) | Cat Data Link (+) |
| 11 | 5 VDC Sensor Power | Sensor Power Output |
| 12 | Lo R Hi F Synchro V | Sourcing Driver Output |
| 13 | - Battery (1) | Battery Return |
| 16 | Front Axle Speed | Hall Effect Input |
| 18 | Rear Axle Speed | Hall Effect Input |
| 20 | Cat Data Link (-) | Cat Data Link (-) |
| 21 | 5 VDC Sensor Return | Sensor Power Return |
| 22 | XMSN Oil Temperature Sensor | Analog Input |
| 23 | - Battery (2) | Battery Return |
| 26 | Location Code 1 | Switch to Ground Input |
| 27 | Location Code 2 | Switch to Ground Input |
| 28 | Location Code 4 | Switch to Ground Input |
| 29 | Variator Flushing Oil Temp | Analog Input |
| 30 | Front Axle Oil Temperature Sensor | Analog Input |
| 31 | + Battery (1) | Battery Power Input |
| 32 | Location Code Enable | Switch to Ground Input |
| 33 | Forward Direction Switch | Switch to Ground Input |
| 34 | Neutral Direction Switch | Switch to Ground Input |
| 35 | Reverse Direction Switch | Switch to Ground Input |
| 36 | Park Brake Pressure Sensor | Analog Input |
| 37 | Brake Accumulator Oil Pressure Sensor | Analog Input |
| 39 | + Battery (2) | Battery Power Input |
| 41 | Armrest Position Switch (N/C) | Switch to Ground Input |
| 42 | Armrest Position Switch (N/O) | Switch to Ground Input |
| 44 | 8V Power Supply | Sensor Power Output |
| 45 | 8V Return | Sensor Power Return |
| 47 | + Battery (3) | Battery Power Input |
| 48 | PPV Pump Control A | Sourcing Driver Output |
| 49 | PPV Pump Control B | Sourcing Driver Output |
| 50 | Driver Return | Sourcing Driver Return |
| 51 | Low High R Synchro Valve | Sourcing Driver Output |
| 52 | Low R High F Synchro V | Sourcing Driver Output |
| 53 | Rear Axle Oil Temperature Sensor | Analog Input |
| 54 | Driver Return | Sourcing Driver Return |
| 55 | Driver Return | Sourcing Driver Return |
| 56 | 10 VDC Return | Sensor Power Return |
| 57 | - Battery (3) | Battery Return |
| 58 | AUX Synchro Valve | Sourcing Driver Output |
| 59 | Synchro Fork Press Supply | Sourcing Driver Output |
| 60 | Driver Return | Sourcing Driver Return |
| 61 | Rear Differential Lock | Sourcing Driver Output |
| 62 | Front Differential Lock | Sourcing Driver Output |
| 64 | Transmission Oil Filter Bypass Switch | Switch to Ground Input |
| 65 | Clutch A | Sourcing Driver Output |
| 66 | Clutch B | Sourcing Driver Output |
| 67 | Left Secondary Steering Solenoid | Sourcing Driver Output |
| 68 | Right Secondary Steering Solenoid | Sourcing Driver Output |
| 69 | +10 VDC Power Supply | Sensor Power Output |
| 70 | - Battery (4) | Battery Return |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
| Contact Description J2(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Neutral Start Input | Switch to Battery Input |
| 2 | Secondary Steering Relay | Sourcing Driver Output |
| 3 | Low F High R Synchro Valve | Sourcing Driver Output |
| 4 | Driver Return | Sourcing Driver Return |
| 5 | Park Brake Solenoid | Sourcing Driver Output |
| 6 | Brake Charging Solenoid | Sourcing Driver Output |
| 7 | Start Relay | Sourcing Driver Output |
| 8 | Driver Return | Sourcing Driver Return |
| 9 | Axle Oil Cooler clutch | Sinking Driver Output |
| 15 | Left Steer Cylinder Position Sensor | PWM Input |
| 16 | Right Steer Cylinder Position Sensor | PWM Input |
| 23 | XMSN Oil Filter Bypass 2 | Switch to Ground Input |
| 24 | Variator Loop A Pressure Sensor | PWM Input |
| 25 | Variator Loop B Pressure Sensor | PWM Input |
| 26 | Left Pedal Position Sensor | PWM Input |
| 27 | Right Pedal Position Sensor | PWM Input |
| 28 | Park Brake Switch N/O | Switch to Ground Input |
| 29 | Park Brake Switch N/C | Switch to Ground Input |
| 31 | Park Brake Switch N/C | Switch to Ground Input |
| 32 | Steering Lever Position Sensor 1 | PWM Input |
| 33 | Secondary Steering Request Input | PWM Input |
| 34 | Steering Lever Position Sensor 3 | PWM Input |
| 38 | Manual Differential Lock N/O | Switch to Ground Input |
| 40 | Speed Range Thumbroller | PWM Input |
| 41 | Brake Accumulator Oil Pressure Sensor | PWM Input |
| 42 | Direction Switch | PWM Input |
| 43 | Direction Switch Redundant | PWM Input |
| 44 | Throttle Lock Set N/O | Switch to Ground Input |
| 46 | Throttle Lock Cancel/Resume N/O | Switch to Ground Input |
| 48 | Steering Lever Position Sensor 2 | PWM Input |
| 49 | High F Low R Fork Position Sensor | PWM Input |
| 50 | High R Low F Fork Position Sensor | PWM Input |
| 51 | Auxiliary Fork Position Sensor | |
| 67 | CAN A Data Link + | CAN Data Link (+) |
| 68 | CAN A Data Link - | CAN Data Link (-) |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
| Contact Description (1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Low Beam Relay | 300 mA Driver 12 |
| 2 | Heated Mirrors Relay | 300 mA Driver 11 |
| 4 | LH Tail Lamps | 300 mA Driver 7 |
| 5 | RH Tail Lamps | 300 mA Driver 5 |
| 6 | Front HID Lights Relay | 300 mA Driver 4 |
| 7 | Rear HID Lights Relay | 300 mA Driver 3 |
| 8 | Front Work Lights Relay | 300 mA Driver 2 |
| 9 | Rear Work Lights Relay | 300 mA Driver 1 |
| 10 | AC Clutch | 2A Driver 7 Output |
| 11 | Quick Coupler Solenoid Engage | 2A Driver 5 Output |
| 12 | Main Power Relay | 2A Driver 3 Output |
| 13 | Low Current Mode Relay | 2A Driver 1 Output |
| 14 | High Beam Relay | 300 mA Driver 13 |
| 15 | HVAC Blower Control Signal | 100 mA SINK DRIVER 4 |
| 16 | Front Wiper On/Off Relay | 300 mA Driver 10 |
| 17 | Rear Wiper On/Off Relay | 300 mA Driver 8 |
| 18 | Beacon Relay | Analog Input 2 |
| 19 | Driver Return | 300 mA 1-8 Return |
| 20 | Left Turn Signal | 2A Driver 8 Output |
| 21 | Right Turn Signal | 2A Driver 6 Output |
| 22 | Quick Coupler Solenoid 2 Disengage | 2A Driver 4 Output |
| 23 | Quick Coupler Solenoid 3 Enable | 2A Driver 2 Output |
| 25 | Water Valve Control Signal | 100 mA SINK DRIVER 3 |
| 29 | Driver Return | 2A Driver 1-4 Return |
| 30 | Recirculation Filter Temperature | Analog Input 2 |
| 31 | Louver Temperature Sensor | Analog Input 1 |
| 32 | Rear Wiper Hi/Low Speed Relay | 300 mA Driver 15 |
| 34 | CAN A Data Link - | CAN Data Link (-) |
| 37 | HVAC Temperature Dial | Analog Input 3 |
| 38 | HVAC Blower Speed Dial | Analog Input 4 |
| 39 | HVAC Evaporator Thermostat | Analog Input 5 |
| 40 | Front Wiper Hi/Low Speed Relay | 300 mA Driver 16 |
| 43 | Driver Return | 2A Driver 5-8 Return |
| 45 | Front Wiper Dial | Analog Input 6 |
| 46 | Rear Wiper Dial | Analog Input 7 |
| 47 | Fuel Level Sensor | Analog Input 8 |
| 48 | HVAC Refrigerant Circuit Switch | SWG INPUT 1 |
| 49 | Rear Washer Switch | SWG INPUT 3 |
| 50 | CAN A Data Link + | CAN Data Link (+) |
| 51 | Auto Climate Control Switch | SWG INPUT 5 |
| 52 | AC On Switch | SWG INPUT 7 |
| 53 | Sensor Supply Return | Sensor Supply Ground |
| 54 | Driver Return | 300 mA 9-16 return |
| 55 | - Battery | + Battery |
| 56 | - Battery | + Battery |
| 57 | - Battery | + Battery |
| 60 | Sensor/Switch Return | Sensor/Switch Ground Return |
| 61 | Front Washer Switch | SWG INPUT 6 |
| 62 | System Wake Up | SWG INPUT 8 |
| 63 | Sensor/Switch Return | Sensor/Switch Ground Return |
| 65 | Sensor Supply | Sensor Supply Output |
| 66 | - Battery | - Battery |
| 67 | - Battery | - Battery |
| 68 | - Battery | - Battery |
| 70 | Keyswitch Input | Keyswitch Input |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |