GUARD AS 8Y9303 - Caterpillar

The solenoid is used to shutoff, release, distribute, or mix fluids in the transmission. Generally, multiple solenoids are located together on a manifold. The solenoid converts electrical energy into magnetic energy by 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 03 Diagnostic code are:
The energize circuit of the solenoid is shorted to the +Battery circuit.
The Transmission ECM has failed (unlikely).Possible causes for an FMI 05 Diagnostic code are:
The energize circuit of the solenoid is open.
The return circuit of the solenoid is open.
The solenoid has failed.
The Transmission ECM has failed (unlikely).Possible causes for an FMI 06 Diagnostic code are:
The energize circuit of the solenoid is shorted to ground.
The solenoid has failed.
The Transmission ECM has failed (unlikely).
Illustration 1 g03123561
Solenoid connections associated with the switch panel
Note: The diagrams above are simplified schematics of the Transmission ECM. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR3186 for the complete schematic.Diagnostic Trouble Code Procedure
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.
Table 2
Troubleshooting Test Steps Values Results
1. Identify Active FMI Code Associated With Solenoid Circuit
A code is present. FMI 03 diagnostic code, proceed to Test Step 2.
FMI 05 diagnostic code, proceed to Test Step 3.
FMI 06 diagnostic code, proceed to Test Step 5.
Begin Process For FMI 03 Troubleshooting HERE
2. Check The Machine Harness For A Short
A. Turn the key start switch