374 Excavator Machine Electronic Control System Sensor Supply - Test - Display Caterpillar


Sensor Supply - Test - Display
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1.1. Display
2.1. Diagnostic Trouble Code Procedure
3.1. FMI 3
4.1. FMI 4
5.1. FMI 6

Display

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the display power supply circuits of the machine.

Table 1
Display (MID 256) 
J1939  DTC  Code Description  System Response 
  145-6  12 VDC Supply: Current Above Normal  The entire display image goes black.
3901-9 Ethernet fault inhibited when active.
The power supply switch will be latched opened, resulting in an open circuit reading on the display output pins. The circuit will remain open until problem resolved and power is cycled. 
  5993-3  12 Volt DC Power Supply #1: Voltage Above Normal  The normal operation with fault present up to 17v. Blue screen on all cameras when above 17v.
5994-3 will be active.
3901-9 ethernet fault inhibited when active.
Power supply switch output will NOT be opened. 
  5993-4  12 Volt DC Power Supply #1: Voltage Below Normal  Blue screens will be displayed on all cameras.
5994-4 will be active.
3901-9 ethernet fault inhibited when active.
Power supply switch output will not be opened. 
  5994-3  12 Volt DC Power Supply #2: Voltage Above Normal  Multiple failures of systems or components associated with this code. 
  5994-4  12 Volt DC Power Supply #2: Voltage Below Normal  Multiple failures of systems or components associated with this code. 

The camera power supply is the voltage output originating from the display connections.



Illustration 1g06339736
Camera and Display Connections

The preceding diagram is a simplified schematic of the camera and display connections. The schematics are electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic to view the entire circuitry of the machine.

Diagnostic Trouble Code Procedure

Table 2
Required Tools 
Tool  Part Number  Description  Qty 
T1  146-4080(1)  Digital Multimeter Group 
8T-3224 Needle Tip Group 
7X-1710 Multimeter Probe Group 
8T-8726 Cable Assembly (Three Pin) (3-Pin Breakout) 
T2  JERD2129  Cat® Electronic Technician (Cat ET) 
Windows-based PC 
466-6258 Communication Adapter Gp 
T3  6V-4148  Connector Repair Kit (Sure Seal) 
T4  190-8900  Connector Field Repair Kit (Deutsch) 
T5  175-3700  Connector Repair Kit Deutsch DT 
(1) This multimeter can use an RS232C cable to connect to a Laptop computer or Dataview tool gp for troubleshooting.

Prior to beginning this procedure, inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure. For sensors powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting procedure.

  1. Identify the active FMI code associated with the components.

  2. Determine which code is present and use the list below to determine which procedure to follow.

  • FMI 3 diagnostic code, proceed to "FMI 3".

  • FMI 4 diagnostic code, proceed to "FMI 4".

  • FMI 6 diagnostic code, proceed to "FMI 6".

FMI 3

Table 3
Check The Voltage At The Cameras 
Troubleshooting Test Steps  Values  Results 
1. Turn the start switch and disconnect switch ON.

2. Disconnect the machine harness connector for the cameras.

3. At the machine harness connector for the cameras, measure the voltage between the camera supply contact and the camera return contact. 
Voltage reading is correct for the cameras.  Result: The voltage reading is correct for the cameras.
Proceed to "Check If The Diagnostic Code Remains" Table 6.


Result: The voltage is greater than the supply for the circuit.
Proceed to "Check The Power Supply At The Display" Table 4. 

Table 4
Check The Power Supply At The Display 
Troubleshooting Test Steps  Values  Results 
1. Turn the start switch and disconnect switch to the OFF position.

2. At the harness connector for the display, use a 151-6320 Removal Tool to remove the supply wire and the camera return wire. The harness connector remains connected to the display.

3. Turn the disconnect switch and the start switch to the ON position.

4. Use the multimeter probes to make contact on the connector pins. Measure the voltage at the display pins between the camera supply contact and camera return contact . 
Voltage reading is correct for the supply.  Result: The voltage is correct. The display power supply is correct. Install the wires and sockets that were removed from the display connector back into the original locations.

Proceed to "Check For A Short In the Harness" Table 5.


Result: The voltage measurement is greater than the supply voltage. The measurement is not correct. The display may have failed.
Proceed to "Check If The Diagnostic Code Remains" Table 6. 

Table 5
Check For A Short In the Harness 
Troubleshooting Test Steps  Values  Results 
1. The cameras remain disconnected from the machine harness.

2. The start switch and disconnect switch remain OFF.

3. Disconnect the machine harness connectors from the display.

4. At the display harness connector, measure the resistance between the supply contact and all the other contacts that are used for the display. 
Each resistance is greater than 5K Ω.  Result: Each resistance is greater than 5K Ω.
Proceed to "Check If The Diagnostic Code Remains" Table 6.


Result: One or more readings less than 5 Ω. There is a short between the signal contact and the circuit with the low resistance.

Repair: Refer to the complete electrical schematic. Examine all the connectors of the machine harness for possible short circuits. Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.
Proceed to "Check If The Diagnostic Code Remains" Table 6. 

Table 6
Check If The Diagnostic Code Remains 
Troubleshooting Test Steps  Values  Results 
1. Reconnect all harness connectors. Return machine to normal operating condition.

2. Turn the start switch and the disconnect switch ON.

3. Clear all diagnostic codes.

4. Operate the machine.

5. Stop the machine and engage the safety lock lever.

6. Check if the diagnostic code is active. 
The diagnostic code is no longer present.  Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation.

STOP.

Result: The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the display may require replacement.

Prior to replacing the display, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time.

STOP. 

FMI 4

Table 7
Check The Cameras 
Troubleshooting Test Steps  Values  Results 
1. Turn the start switch and disconnect switch to the ON position.

2. Observe the status of the diagnostic code as each camera is disconnected. 
The FMI 4 diagnostic code is no longer active when one of the cameras on the supply circuit is disconnected.  Result: The diagnostic code is not active when one of the cameras in the supply circuit is disconnected. The power supply circuit is correct.

Repair: Repeat this test step to determine the camera that causes the problem. Replace the camera that is causing the problem.
Proceed to "Check If The Diagnostic Code Remains" Table 10.


Result: The diagnostic code is still active. Disconnecting the cameras in the circuit did not affect the status of the diagnostic code.
Proceed to "Check The Signal Circuit For A Short To Ground" Table 8. 

Table 8
Check The Signal Circuit For A Short To Ground 
Troubleshooting Test Steps  Values  Results 
1. Turn the start switch and the disconnect switch OFF.

2. Disconnect the harness connectors from the display.

3. Measure the resistance between the power supply contact and frame ground.

4. Measure the resistance between the power supply contact and all the other contacts that are used for the display. 
Each resistance is greater than 5K Ω.  Result: Each resistance is greater than 5K Ω. The harness circuit is correct.
Proceed to "Check The Power Supply At The Display" Table 9.


Result: The resistance is less than 5 Ω. The power supply circuit is shorted to ground. The short circuit exists between the power supply circuit and the circuit with the low-resistance measurement.

Repair: Repair or replace the machine harness.
Proceed to "Check If The Diagnostic Code Remains" Table 10.
 

Table 9
Check The Power Supply At The Display 
Troubleshooting Test Steps  Values  Results 
1. Turn the start switch and disconnect switch to the OFF position.

2. At the harness connector for the display, use a 151-6320 Removal Tool to remove the supply wire and the camera return wire. The harness connector remains connected to the display.

3. Turn the disconnect switch and the start switch to the ON position.

4. Use the multimeter probes to make contact on the connector pins. Measure the voltage at the display pins between the camera supply contact and camera return contact . 
Voltage reading is correct for the supply.  Result: The voltage is correct. The display power supply is correct. Install the wires and sockets that were removed from the display connector back into the original locations.
Proceed to "Check If The Diagnostic Code Remains" Table 10.


Result: The voltage measurement is less than the supply voltage. The measurement is not correct. The display has failed.
Proceed to "Check If The Diagnostic Code Remains" Table 10.
 

Table 10
Check If The Diagnostic Code Remains 
Troubleshooting Test Steps  Values  Results 
1. Reconnect all harness connectors. Return machine to normal operating condition.

2. Turn the start switch and the disconnect switch ON.

3. Clear all diagnostic codes.

4. Operate the machine.

5. Stop the machine and engage the safety lock lever.

6. Check if the diagnostic code is active. 
The diagnostic code is no longer present.  Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation.

STOP.

Result: The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the display may require replacement.

Prior to replacing the display, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time.

STOP. 

FMI 6

Table 11
Check For A Short To Ground 
Troubleshooting Test Steps  Values  Results 
1. Turn the start switch and the disconnect switch OFF.

2. Disconnect the machine harness from the display.

3. At the display harness connector, measure the resistance between frame ground and the contact for the supply of the camera. 
The resistance is greater than 5K Ω  Result: The harness circuit resistance is correct. Verify that the diagnostic code is present.

Repair: Perform this procedure again. Also, recheck if the diagnostic code is active.
Proceed to "Check If The Diagnostic Code Remains" Table 13.


Result: The resistance is less than 5 Ω. The machine harness or a camera has failed.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.
Proceed to "Disconnect Each Camera And Check For A Short To Ground" Table 12. 

Table 12
Disconnect Each Camera And Check For A Short To Ground 
Troubleshooting Test Steps  Values  Results 
1. Turn the start switch and the disconnect switch OFF.

2. Disconnect the cameras from the machine harness one at a time.

3. After a camera is disconnected, check the resistance from frame ground to camera supply of the machine harness connector for the display.

Repeat for each camera. 
The resistance is greater than 5K Ω,  Result: The resistance is greater than 5K Ω. The harness circuit resistance is correct. The camera that was last disconnected has failed.

Repair: Replace the camera that caused the short.
Proceed to "Check If The Diagnostic Code Remains" Table 13.


Result: Resistance is less than 5 Ω after all the cameras have been disconnected from the machine harness. The machine harness is shorted to ground.

Repair: Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.
Proceed to "Check If The Diagnostic Code Remains" Table 13.
 

Table 13
Check If The Diagnostic Code Remains 
Troubleshooting Test Steps  Values  Results 
1. Reconnect all harness connectors. Return machine to normal operating condition.

2. Turn the start switch and the disconnect switch ON.

3. Clear all diagnostic codes.

4. Operate the machine.

5. Stop the machine and engage the safety lock lever.

6. Check if the diagnostic code is active. 
The diagnostic code is no longer present.  Result: The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation.

STOP.

Result: The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the display may require replacement.

Prior to replacing the display, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time.

STOP. 

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