DISC AS 4692179 - Caterpillar

The solenoid is used to shutoff, release, distribute, or mix fluids on the machine. Generally, multiple solenoids are located together on a manifold. The solenoid converts electrical energy into magnetic energy, moving a spool located inside the housing of the valve. A spring is used to hold the spool in position until the solenoid is energized.The magnetic force that acts on the valve spool is created when a coil inside the solenoid is energized.
Possible Causes for an FMI 3 Diagnostic code are:
The harness is shorted.
The Machine ECM has failed. A failure of the ECM is unlikely.Possible causes for an FMI 4 Diagnostic code are:
There is an open in the circuit.
The solenoid has failed.
The Machine ECM has failed. A failure of the ECM is unlikely.Note: 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.
Illustration 1 g02997636
Machine ECM J1 Solenoid Return Connections
Illustration 2 g02997657
Implement ECM Solenoid Return ConnectionsNote: The diagram above is a simplified schematics of 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, UENR0072 for the complete schematic.
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 4 diagnostic code, proceed to Test Step 3.    
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. Disconnect the harness connection at the ECM.
D. Measure the resistance of solenoid signal contact to all other ECM connections.    
Each reading is greater than 5K Ω.    
OK - All resistance readings are greater than 5K Ω .
Proceed to Test Step 4.
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 4 Troubleshooting HERE    
3. Check The Machine Harness For An Open
A. Turn the key start switch and the disconnect switch OFF.
B. Disconnect the solenoid from the machine harness.
C. Disconnect the harness connection at the ECM.
D. Connect a jumper wire at the two contacts at the solenoid end of the wiring harness.
E. At the ECM side