320D3 GC Excavators Machine Electronic Control System Relay - Test Caterpillar


Relay - Test
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1.1. Machine ECM
2.1. Diagnostic Trouble Code Procedure
3.1. FMI 3
4.1. FMI 6

Machine ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the relays of the machine.

Table 1
Machine ECM (MID 299) 
J1939  CDL  Code Description  System Response 
  444-3  Starter Motor Relay : Voltage Above Normal  Starter motor will be inoperable. 
  444-5  Starter Motor Relay : Current Below Normal  Starter motor will be inoperable. 
  444-6  Starter Motor Relay : Current Above Normal  Starter motor will be inoperable. 
  781-3  Lighting Relay : Voltage Above Normal  Related lighting system will be ON continuously. 
  781-6  Lighting Relay : Current Above Normal  Related lighting system will be ON continuously. 
  2912-3  Front Wiper Speed Control Relay : Voltage Above Normal  Wiper system will not function. 
  2912-6  Front Wiper Speed Control Relay : Current Above Normal  Wiper system will not function. 
  3634-3  Boom Light Relay : Voltage Above Normal  Related lighting system will be ON continuously. 
  3634-6  Boom Light Relay : Current Above Normal  Related lighting system will be ON continuously. 

A relay is a component that uses a small amount of electrical current to control the state of a circuit. The circuit is either opened or closed.



Illustration 1g06575523
Machine ECM and Switch Panel Relay schematic

The diagram above is a simplified schematic of the Machine ECM and Switch Panel connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, M0116913 for 320D3 GC excavator electrical systems.

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 
538-5051 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. Check the wiring harness for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a 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 6 Diagnostic code, proceed to "FMI 6".

FMI 3

Table 3
Check The Machine Harness For A Short 
Troubleshooting Test Steps  Values  Results 
1. Turn the key start switch and disconnect switch to the OFF position.

2. Disconnect the relay from the harness.

3. Disconnect the ECM machine harness connectors.

4. At the ECM machine harness connector, measure the resistance between the signal contact and all other contacts that are used in the ECM. 
Each resistance measurement is greater than 5KΩ.  Result: All resistance measurements are greater than 5K Ω.

Proceed to "Check If The Diagnostic Code Remains" Table 4.

Result: One or more readings are less than 5 Ω.

Repair: A short exists between the signal contact and the circuit with the low resistance. Repair or replace the machine harness.

Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit.

Proceed to "Check If The Diagnostic Code Remains" Table 4. 

Table 4
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 key start switch and the disconnect switch to the ON position.

3. Clear all diagnostic codes.

4. Operate the machine.

5. Stop the machine and engage the safety lock.

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 ECM may require replacement.

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

Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced.

STOP

FMI 6

Table 5
Check The Relay 
Troubleshooting Test Steps  Values  Results 
1. Turn the key start switch and disconnect switch to the ON position.

2. Observe the status of the diagnostic code.

3. Disconnect the relay from the machine harness. 
The FMI 6 changes to FMI 5 when the relay is disconnected.  Result: FMI 6 changes to FMI 5 when the relay is disconnected. The harness is correct. The relay has failed.

Repair: Repair or replace the relay.

Proceed to "Check If The Diagnostic Code Remains" Table 7.

Result: The diagnostic code remains active.

Proceed to "Check The Return Circuit For A Short To Ground" Table 6. 

Table 6
Check The Return Circuit For A Short To Ground 
Troubleshooting Test Steps  Values  Results 
1. Turn key switch and disconnect switch to the OFF position.

2. The relay remains disconnected from the machine harness.

3. Disconnect the machine harness connectors from the ECM.

4. At the ECM machine harness connector, measure the resistance between the signal contact and all other contacts that are used in the ECM.
 
Each resistance measurement is greater than 5K Ω.  Result: Each resistance measurement is greater than 5K Ω. The machine harness is correct.

Proceed to "Check If The Diagnostic Code Remains" Table 7.

Result: Each resistance measurement is not greater than 5K Ω. A short circuit exists between the signal circuit and the circuit with the low-resistance measurement.

Repair: Repair or replace the machine harness.

Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit.

Proceed to "Check If The Diagnostic Code Remains" Table 7. 

Table 7
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 key start switch and the disconnect switch to the ON position.

3. Clear all diagnostic codes.

4. Operate the machine.

5. Stop the machine and engage the safety lock.

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 ECM may require replacement.

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

Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced.

STOP

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