FILM 2153852 - Caterpillar

Machine ECM
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the system voltage circuits of the machine.
Table 1
Machine ECM (MID 299)
DTC Code Description System Response
168-5 Electrical System Voltage : Current Below Normal Numerous machine system failures can be expected when this code is active. The electrical power supply connections are the connections between the alternator and battery that power the control modules.Possible Causes for an FMI 5 diagnostic code are:
A charging system component has failed.
The machine harness is open.
The Machine ECM has failed. A failure of the ECM is unlikely.
Illustration 1 g03668215
Machine ECM electrical system connections
Note: The diagram above is a simplified schematic of the System Voltage Machine ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the Electrical System Schematic, UENR3969 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.
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 5 diagnostic code, proceed to Table 2.
Table 2
FMI 5 Troubleshooting
Troubleshooting Test Steps Values Results
1. Check For An Open Circuit
A. Turn key start switch and disconnect switch OFF.
B. Disconnect the wire at alternator terminal labeled “W”.
C. Disconnect the same wire from the Switch Panel (see schematic above).
D. Connect one end of the wire to a know good ground.
E. Measure the resistance of the wire at the open end of the connector.
The resistance is 5 Ω or less. OK - The machine harness appears to work correctly. Either the alternator is not working correctly or the ECM may be recording the diagnostic code incorrectly.
Proceed to Test Step 2.
NOT OK - The resistance measurement is greater than 5K Ω. The wire in the harness between the alternator and the Switch Panel is open or damaged.
Repair: Repair or replace the wiring harness.
Note: A resistance that is greater than 5 π 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.
Proceed to Test Step 4.
2. Check The Charging System At High Idle
A. Turn key start switch and disconnect switch ON.
B. Clear all active diagnostic codes.
C. Start the engine. Run engine at HIGH idle.
D. Enter the diagnostic menu on the monitor.
E. Observe status of diagnostic code.
Diagnostic code is no longer active. OK - Diagnostic code is no longer active.
Proceed to Test Step 3.
NOT OK -