GUARD G. 4B7964 - Caterpillar

Possible Causes for an FMI 3 diagnostic code are:
The power circuit of the solenoid is shorted to a higher voltage source.
The solenoid has failed.
The ECM has failed. This situation is unlikely.Possible Causes for an FMI 5 diagnostic code are:
The energize circuit of the solenoid is open.
The return circuit of the solenoid is open.
The solenoid has failed.
The ECM has failed. This situation is unlikely.Possible Causes for an FMI 6 diagnostic code are:
A short to ground exists.
The solenoid has failed.
The ECM has failed. This situation is unlikely.
Illustration 1 g03644416
Connections of the Quick Coupler SolenoidNote: The diagram above is a simplified schematic of the Implement ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, KENR5564 for the complete schematic.Diagnostic Trouble Code Procedure
Before performing this procedure, inspect the harness connectors that are involved in the 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 this diagnostic code is active before performing this procedure.
Table 2
Troubleshooting Test Steps    Values    Results    
1. Identify Active FMI Code Associated With Solenoid Circuit    
Code present.     FMI 3 diagnostic code, proceed to Test Step 2.
FMI 5 diagnostic code, proceed to Test Step 3.
FMI 6 diagnostic code, proceed to Test Step 5.    
Begin Process For FMI 3 Troubleshooting HERE    
2. Check The Machine Harness For A Short
A. Turn the key start switch and the disconnect switch OFF.
B. Disconnect the harness connection at solenoid.
C. If the solenoid is connected to ECM, disconnect J1 and J2 connectors from ECM. If the solenoid is connected to the switch panel, disconnect all switch panel connectors.
D. Measure the resistance of solenoid signal contact to all J1 and J2 connectors.    
Each reading is greater than 5K Ω.     OK - All resistance readings are greater than 5K Ω .
Proceed to Test Step 7.
NOT OK - 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 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.
STOP    
Begin Process For FMI 5 Troubleshooting HERE    
3. Check The Solenoid.
A. Turn the key start switch and the disconnect switch OFF.
B. Disconnect the solenoid from the machine harness.
C. Place a jumper wire between contact 1 and contact 2, at the harness connector for the solenoid.
D. Turn the key start switch and the disconnect switch ON. Do not start the engine.
E. As the jumper is removed and connected to the contacts, observe any code change.    
The code changes to FMI 6