320D3 GC Excavators Machine Electronic Control System Connector Contact Description Caterpillar


Connector Contact Description
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1.1. ECM Pull Up Voltage
2.1. ECM Pull Down Voltage
3.1. Inputs
4.1. Outputs
5.1. Input/Output
6.1. Machine ECM
7.1. Switch Panel

The Electronic Control Modules (ECM) make decisions based on input data information and programming parameters that have been flashed to the ECM memory. 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 circuits and the internal output circuits of the ECM are connected to the machine wiring harness by a contact connector (J1).

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 AVSpare before replacing the ECM. Replace the ECM only after all the other possible causes of a particular problem have been investigated.

ECM Pull Up Voltage

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

ECM Pull Down Voltage

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.

Inputs

The machine has several different types of input devices. The ECM receives machine status information from the input devices. The ECM then determines the correct output action that is needed 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 Machine ECM is listed in the tables for the connectors.

Outputs

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 Machine ECM are listed in the tables for the connectors.

Input/Output

Communication between the Machine 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 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 Machine 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 Machine ECM is 299.

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.

Machine ECM

Table 1
Contact Description for Connector J1 (1) 
No.  Function  Type 
Ground  Ground 
PRV 4-7 Return  PRV Return 
+ Battery  Battery (+) 
PRV 1-3 Return  PRV Return 
CAN 2 + : Machine Data Link  CAN 2 + 
CAN 1 + : J1939  CAN 1 + 
10  Air Cleaner Switch  Switch To Ground 1 
15  5V Supply  5V Supply 1 
17  Atmosphere Pressure Sensor  Analog Active Input 
22  Hydraulic Lock Solenoid  PRV 1 
23  Swing Brake Solenoid  PRV 2 
24  High Hydraulic Oil Temperature Indicator  PRV 3 
27  CAN 2 - : Machine Data Link  CAN 2 - 
28  CAN 1 - : J1939  CAN 1 - 
29  One Touch Low Idle Switch  Switch To Ground 8 
30  Travel Pressure Switch  Switch To Ground 9 
32  Engine Oil Pressure Sensor  Analog Active Input 
34  Analog & PWM Return 1  Analog & PWM Return 1 
35  Hydraulic Oil Temperature Sensor  Analog Passive Input 1 
36  Coolant Temperature Sensor_2  Analog Passive Input 2 
37  Analog Return  Analog Return 
39  Engine Speed Command  Low Sink 
40  R-Term  R-Term 
41  Key Switch  Key Switch 
42  Engine ECO Mode Indicator  PRV 4 
43  Low Engine Oil Pressure Indicator  PRV 5 
49  Switch To Ground Return 1  Switch To Ground Return 1 
51  Implement Pressure Switch  Switch To Ground 5 
58  Hydraulic Lock Cancel Switch  Switch To Battery 1 
60  Start Detection  Input\Output 
61  Neutral Start Relay  PRV 6 
73  Engine Speed Command Read  PWM Input 5 
78  Engine Speed Sensor  VR+ 
(1) Contacts that are not listed are not used.

Switch Panel

Table 2
Contact Description for Connector F-C302 
No.  Function  Type 
Machine CAN Data Link +  CAN + 
Machine CAN Data Link +  CAN - 
Washer  LCSD 
Wiper Int - 3  LCSD 
Wiper Int - 6  LCSD 
Wiper Low  LCSD 

Table 3
Contact Description for Switch Panel Connector F-C303 
No.  Function  Type 
+B  +Battery 
GND  Ground 
Key Switch 1  Key Switch 
Action Alarm  On/Off 
10  B+  Unswitched Battery 
15  Chassis/Cab Lamp Relay  Relay 
16  Boom Lamp Relay  Relay 

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