TUBE AS 4Z8750 - Caterpillar

This diagnostic code is associated with the output driver of the MSS3s ECM. This code is recorded if voltage is present on the output driver circuit when the MSS is armed. This circuit is not used on all machines.Note: For CID 1391 output driver #1 check for the presence of wires at contact 11 and contact 58 before you perform the procedure.Note: For CID 1392 output driver #2 check for the presence of wires at contact 5 and contact 52 before you perform the procedure.Possible causes for an FMI 03 diagnostic code are:
There is a problem with the software in the ECM
There is a short to the +battery circuit in the wiring harness
The ECM has failed. A failure of the ECM is unlikelyPossible causes for an FMI 04 diagnostic code are:
The wiring in the machine harness has failed
The driven component in the circuit has failed
The ECM has failed. A failure of the ECM is unlikelyNote: The locations of the components of the MSS will vary between machines. If the MSS was installed by a Caterpillar dealer, consult the installation instructions for component locations. If the MSS was an attachment that was installed at the factory, consult the electrical schematic for that machine.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. Ensure that the Charging System is functioning properly. 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.
Identify the active FMI code associated with the components.
Determine which code is present and use the list below to determine which procedure to follow.
FMI 03 diagnostic code, proceed to Table 2
FMI 04 diagnostic code, proceed to Table 3
Table 2
FMI 03 Troubleshooting
Troubleshooting Test Steps Values Results
1. FLASH THE ECM
A. Load the latest software file for the MSS into the ECM. Refer to Testing and Adjusting, "Electronic Control Module (ECM) - Flash Program".
B. Clear the diagnostic code log.
C. Start the machine and operate the machine.
D. Determine if FMI 03 is present.
FMI 03 is present. OK - FMI 03 is present.
Go to Test Step 2.
NOT OK - The diagnostic code was caused by a problem in the software.
STOP.
2. TEST THE MACHINE HARNESS
A. The key start switch must be in the OFF position.
B. Disconnect the machine harness from the MSS3s ECM.
C. Measure the voltage between the pins on the connector for the MSS3s ECM.
a. For CID 1391 Driver #1 pins 11 and 58.
b. For CID 1392 Driver #2 pins 5 and 52.
Voltage is present. OK - Voltage is present between the pins. The wiring harness is shorted.
Repair: Repair or replace the machine harness.
STOP.
NOT OK - Voltage is not present between the pins.
Go to Test