COMMON AR 3688477 - Caterpillar

Machine ECM
The following is a list of Diagnostic Trouble Codes (DTC) associated with the system voltage circuit 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.    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 g03694639
Machine ECM electrical system connectionsNote: The diagram above is a simplified schematic of the System Voltage connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR5805 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. 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     Code present     FMI 5 diagnostic code, proceed to Test Step 2.    
Begin Process For DTC 168-5 Troubleshooting HERE    
2. 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 3.
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 greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit.
STOP    
3. Check The Charging System At High