374 Excavator 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 1
7.1. Machine ECM 2
8.1. Machine ECM 3
9.1. Body Control Modules

The Machine ECM will make decisions that are 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 two contact connectors (J1 and J2).

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 and 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 Machine ECM 1 is 299. The MID for Machine ECM 2 is 432.

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 1

Table 1
Machine ECM #1 Connector J1 Contact Descriptions (1) 
No.  Function  Type 
Ground  Ground 
PRV 8-10 Return  PRV Return 
PRV 4-7 Return  PRV Return 
+ Battery  Battery (+) 
PRV 1-3 Return  PRV Return 
J1939 for CGC  CAN3 + 
Machine Can Data Link  CAN2 + 
J1939  CAN1 + 
10  Location Code1  Switch To Ground 1 
15  5V Supply  5V Supply 1 
20  8V Supply  8V Supply 1 
22  Hydraulic Lock Solenoid  PRV 1 
24  EH - Boom Up  PRV 3 
26  J1939 for CGC  CAN3 - 
27  Machine Can Data Link  CAN2 - 
28  J1939  CAN1 - 
29  Left Joystick Switch 3  Switch To Ground 8 
30  Left Joystick Switch 4  Switch To Ground 9 
32  Pump 1 Displacement Sensor  PWM/Freq In 23 
33  Pump 2 Displacement Sensor  PWM/Freq In 24 
34  Analog & PWM Return 1  Analog & PWM return 1 
35  Hydraulic Oil Temperature Sensor  Analog Passive In 1 
37  Fuel Level Sensor  Fuel Level Sender 
38  Analog & PWM Return 2  Analog & PWM return 2 
41  Key Switch  Key Switch 
42  EH - Boom Down  PRV 4 
43  EH - Stick Out  PRV 5 
44  Ether 2 TX +  Ethernet 
45  Ether 2 TX -  Ethernet 
46  Ether 2 RX +  Ethernet 
47  Ether 2 RX -  Ethernet 
49  STG Return 1  STG Return 1 
50  Location Code Enable/Disable  Switch To Ground 4 
52  Seat Switch  Switch To Ground 6 
53  Left Joystick Switch 2  Switch To Ground 7 
54  Pump 1 Pressure Sensor  PWM/Freq In 1 
55  Pump 2 Pressure Sensor   PWM/Freq In 2 
56  Stick Cylinder Head Pressure Sensor  PWM/Freq In 3 
57  Stick Cylinder Rod Pressure Sensor  PWM/Freq In 4 
58  Hydraulic Lock Status  Switch To Battery 1 
59  Start Detection / Neutral Started Status  Switch To Battery 2 
60  Fan Diagnostic  Switch To Battery 3 
61  Stick In  PRV 6 
62  Bucket Curl  PRV 7 
63  Ether 1 TX +  Ethernet 
64  Ether 1 TX -  Ethernet 
65  Ether 1 RX +  Ethernet 
66  Ether 1 RX -  Ethernet 
67  Capsule Filter Plugged Switch  Switch To Ground 10 
68  STG Return 2  STG Return 2 
69  Left Joystick Switch 5 (SVAB)  Switch To Ground 11 
70  Right Joystick Switch 5 (SVAB)  Switch To Ground 12 
71  Bucket Cylinder End Detection  Switch To Ground 12 
73  Boom Cylinder Head Pressure Sensor  PWM/Freq In 5 
74  Boom Cylinder Rod Pressure Sensor  PWM/Freq In 6 
75  Swing Sensor A  PWM/Freq In 7 
76  Swing sensor B  PWM/Freq In 8 
77  Bucket Cylinder Head Pressure Sensor  PWM/Freq In 16 
79  EH - Bucket Un-curl  PRV 8 
80  EH - Swing left  PRV 9 
81  EH -Swing Right  PRV 10 
(1) Contacts that are not listed are not used.

Table 2
Machine ECM #1 Connector J2 Contact Descriptions (1) 
No.  Function  Type 
82  Right Joystick Switch 1  Switch To Ground 15 
83  Right Joystick Switch 2  Switch To Ground 16 
84  Engine Start Switch (PTS)  Switch To Battery 4 
85  Right Joystick Switch 3  Switch To Ground 17 
86  Right Joystick Switch 4  Switch To Ground 18 
87  Analog & PWM Return 4  Analog & PWM Return 4 
88  EP Pump Solenoid 1  PRV 17 
89  EP Pump Solenoid 2  PRV 18 
90  Machine ECM data sharing network (MDTP)  CAN4 + 
91  Machine ECM data sharing network (MDTP)  CAN4 - 
92  8V Supply  8V Supply 2 
93  STG Return 3  STG Return 3 
95  Bucket Cylinder Rod Pressure Sensor  PWM/Freq In 15 
96  Bypass Cut 1  PRV 15 
97  Bypass Cut 2  PRV 16 
98  Joystick RH-X  PWM/Freq In 11 
99  Joystick RH-Y  PWM/Freq In 12 
100  Analog & PWM Return 3  Analog & PWM Return 3 
101  5V Supply  5V Supply 2 
102  Swing Left Pressure Sensor  PWM/Freq In 13 
103  Swing Right Pressure Sensor  PWM/Freq In 14 
104  Stick 2 In  PRV 13 
105  Stick 2 Cut  PRV 14 
110  Joystick LH-X  PWM/Freq In 9 
111  Joystick LH-Y  PWM/Freq In 10 
112  Boom 2 Up Solenoid  PRV 11 
113  Stick 2 Out Solenoid  PRV 12 
114  PRV 17-18 Return  PRV 17-18 Return 
117  PRV 13-14 Return  PRV 13-14 Return 
118  PRV 15-16 Return  PRV 15-16 Return 
119  PRV 11-12 Return  PRV 11-12 Return 
(1) Contacts that are not listed are not used.

Machine ECM 2

Table 3
Machine ECM #2 Connector J1 Contact Descriptions (1) 
No.  Function  Type 
Ground  Ground 
PRV 8-10 Return  PRV Return 
PRV 4-7 Return  PRV Return 
+ Battery  Battery (+) 
PRV 1-3 Return  PRV Return 
CGC: Can 3 +  CAN3 + 
J1939: Can 1 +  CAN1 + 
11  Location Code2  Switch To Ground 2 
15  5V Supply  5V Supply 
20  8V Supply  8V Supply 1 
22  ATT Stem 2 Retract EPRV  PRV 1 
23  ATT Stem 2 Extend EPRV  PRV 2 
24  ATT Stem 1 Retract EPRV  PRV 3 
26  CGC  CAN3 - 
28  J1939  CAN1 - 
34  Analog & PWM Return 1  Analog & PWM Return 1 
41  Key Switch  Key Switch 
42  Att Stem 2 Extend EPRV  PRV 4 
43  Att Stem 3 Retract EPRV  PRV 5 
44  Ether 1 TX +  Ethernet 
45  Ether 1 TX -  Ethernet 
46  Ether 2 RX +  Ethernet 
47  Ether 2 RX -  Ethernet 
49  STG Return 1  STG Return 1 
50  Location Code Enable/Disable  Switch To Ground 4 
52  Quick Coupler Switch  Switch To Ground 6 
54  CTWT Removal Cylinder Pressure Sensor  PWM/Freq In 1 
56  Travel Left Pedal Sensor  PWM/Freq In 3 
57  Travel Right Pedal Sensor  PWM/Freq In 4 
58  +B for PRV1 power supply  Switch To Battery 1 
61  Att Stem 3 Extend EPRV  PRV 6 
62  Hydraulic Motor Fan EPRV  PRV 7 
63  Ether 1 TX +  Ethernet 
64  Ether 1 TX -  Ethernet 
65  Ether 1 RX +  Ethernet 
66  Ether 1 RX -  Ethernet 
73  Thumb Wheel 1 - LH  PWM/Freq In 5 
75  Thumb Wheel 1 - RH  PWM/Freq In 7 
79  Boom 2 Down Solenoid  PRV 8 
80  Att Line 1 RERV  PRV 9 
81  Att Line 2 RERV  PRV 10 
(1) Contacts that are not listed are not used.

Table 4
Machine ECM Connector J2 Contact Descriptions (1) 
No.  Function  Type 
87  Analog & PWM Return 4  Analog & PWM Return 4 
88  EH - Travel Right Fwd  PRV 13 
89  EH - Travel Right Rev  PRV 14 
90  Machine ECM Data Sharing  CAN4 + 
91  Machine ECM Date Sharing  CAN4 - 
92  8v Supply  8v Supply 
96  QCPLR Lock/Unlock Solenoid 2  PRV 15 
97  Travel Left Reverse Solenoid  PRV 12 
98  Aux Pedal RH  PWM/Freq In 15 
99  Bucket Angle  PWM/Freq in 12 
104  QCPLR Lock/Unlock Solenoid 1  PRV 13 
105  Left Travel Forward Solenoid  PRV 11 
110  Squeeze Head End Pressure Sensor  PWM/Freq In 9 
111  Squeeze Rod End Pressure Sensor  PWM/Freq In 10 
112  Swing Brake Solenoid (On/Off)  PRV 11 
113  Boom Down Ele Check  PRV 12 
114  PRV 17-18 Ret  PRV 17-18 Ret 
117  PRV 13-14 Ret  PRV 13-14 Ret 
118  PRV 15-16 Ret  PRV 15-16 Ret 
119  PRV 11-12 Ret  PRV 11-12 Ret 
(1) Contacts that are not listed are not used.

Machine ECM 3

Table 5
Machine ECM #3 Connector J1 Contact Descriptions (1) 
No.  Function  Type 
Ground  Ground 
PRV 4-7 Return  PRV Return 
+ Battery  Battery (+) 
PRV 1-3 Return  PRV Return 
Machine Can Data Link  CAN2 + 
J1939  CAN1 + 
23  Fore Boom Extend Solenoid  PRV 
24  Fore Boom Retract Solenoid  PRV 
27  Machine Can Data Link  CAN2 - 
28  J1939  CAN1 - 
41  Key Switch  Key Switch 
42  Boom Coupler Lock Solenoid  PRV 
43  Boom Coupler Unlock Solenoid  PRV 
48  STG 3  Switch To Ground 
50  STG 4  Switch To Ground 
58  STB 1  Switch To Battery 
61  Tilt Cab Up Solenoid  PRV 
62  Tilt Cab Down Solenoid  PRV 
(1) Contacts that are not listed are not used.

Body Control Modules

Table 6
BCM 1 Connector Contact Descriptions (1) 
No.  Function  Type 
-B  Power Supply 
Driver Return 9-12  PRV Return 
Driver Return 5-8  PRV Return 
+B  Power Supply 
Driver Return 1-4  PRV Return 
J1939  CAN2 + 
Machine Can Data Link (Local Can)  CAN1 + 
13  CTWT Removal Switch  CTWT Removal Switch 
14  CTWT SW UP  CTWT SW UP 
16  Engine Start Button LED (Green)  Low Current Driver 1 
17  Engine Start Button LED (Red)  Low Current Driver 2 
18  ECM (Wake Up)  Low Current Driver 3 
19  Dome Light / Foot Light  Low Current Driver 4 
21  Wake Up Input 1  Wake up 1 (Switch To Battery) 
22  Wake Up Input 3  Wake up 3 (Switch To Ground) 
23  Main power relay  On/Off Driver / Relay 1 
24  M-ECM (Primary) Key Switch  On/Off Driver / Relay 2 
27  J1939  CAN2 - 
28  Machine Can Data Link (Local Can)  CAN1 - 
29  Travel Alarm Cancel Switch  Switch To Ground 7 
30  Washer Fluid Level Switch  Switch To Ground 8 
31  STG Return 7-8  STG Return 7-8 
32  CTWT SW Down  CTWT SW Down 
33  Beacon Switch  Beacon Switch 
36  Refuel Pump Relay  Low Current Driver 5 
37  Engine Key Switch  Low Current Driver 6 
38  Boom Light Relay  Low Current Driver 7 
39  Chassis / Cab Light Relay  Low Current Driver 8 
40  Wake Up Input 2  Wake up 2 (Switch To Ground) 
41  Key Switch (On-Detect)  Key Switch 
42  Straight Travel Solenoid  On/Off Driver / Relay 3 
43  QCPLR Solenoid  On/Off Driver / Relay 4 
44  Electric Fan Control 1  High side PWM output 1 
45  Electric Fan Control 2  High side PWM output 2 
59  Heavy Lift Solenoid  On/Off Driver / Relay 5 
60  Travel Alarm  On/Off Driver / Relay 6 
61  Caution Lamp (for Crane)  On/Off Driver / Relay 7 
62  Boom Up Electric Check Solenoid  On/Off Driver / Relay 8 
63  Electric Fan Control 3  High side PWM output 3 
64  Seat Belt Caution  On/Off Driver / Relay 9 
67  Att Hydraulic Oil Filter Switch  Switch To Ground 5 
68  STG Return 5-6  Switch To Ground Return 
69  Refuel Start Switch  Switch To Ground 6 
77  Key Switch (Off-Detect)  Switch To Battery 8 
78  Travel Speed Solenoid  On/Off Driver / Relay 10 
79  Fine Swing Solenoid  On/Off Driver / Relay 11 
80  Engine Start Signal  On/Off Driver / Relay 12 
81  Hydraulic Reverse Fan Solenoid  On/Off Driver / Relay 13 
(1) Contacts that are not listed are not used.

Table 7
BCM 2 Connector Contact Descriptions (1) 
No.  Function  Type 
-B  Power Supply 
Driver Return 5-8  PRV Return 
+B  Power Supply 
Driver Return 1-4  PRV Return 
J1939  CAN + 
Machine Can Data Link (Local Can)  CAN + 
23  Sky Wiper relay  On/Off Driver / Relay 1 
24  M-ECM (Primary) Key Switch  On/Off Driver / Relay 2 
27  J1939  CAN - 
28  Machine Can Data Link (Local Can)  CAN - 
41  Key Switch  Key Switch 
42  Tilt Cab Alarm  On/Off Driver / Relay 3 
43  Free Rotate  On/Off Driver / Relay 4 
48  Location Code 3  Switch To Ground 
49  STG Return 3-4  STG Return 3-4 
50  Location Code Enable/ Disable  Switch To Ground 
59  Stability Indicator (Green)  On/Off Driver / Relay 5 
60  Stability Indicator (Yellow)  On/Off Driver / Relay 6 
61  Stability Indicator (Red)  On/Off Driver / Relay 7 
(1) Contacts that are not listed are not used.

Information System:

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374 Excavator Fuses - Replace
395 Excavator Service Interval Chart
374 Excavator Capacities (Refill)
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395 Excavator Hydraulic System Oil Filter - Replace
374 Excavator Engine and Machine Warm-Up
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374 Excavator ARD Spark Plug - Clean - Emission-Related Component
395 Excavator Machine Systems Stick Bearings and Seals - Remove and Install
395 Excavator Machine Systems Swing Gear and Bearing - Install
374 Excavator Machine Electronic Control System Sensor Supply - Test - Display
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395 Excavator Machine Systems Boom - Remove and Install
374 Excavator Fuses - Replace
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