538, 548 and 558 Forest Machine Electrical Power Supply - Test Caterpillar


Electrical Power Supply - Test
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538, 548 and 558 Forest Machine [M0066266]
ELECTRICAL AND STARTING SYSTEM
BATTERY GP
538, 548 and 558 Forest Machine Electrical Power Supply - Test
1.1. Machine ECM
2.1. Diagnostic Trouble Code Procedure

Machine ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are 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 1g06026961
Machine ECM electrical system connections

The preceding diagram is a simplified schematic of the System Voltage connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic to view the entire circuitry of the machine.

Diagnostic Trouble Code Procedure

Prior to beginning this procedure, inspect the harness connectors 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.

  1. Identify the active FMI code associated with the components.

  2. 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 the key start switch and disconnect switch to the OFF position.

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 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.

Proceed to Test Step 4. 
2. Check The Charging System At High Idle

A. Turn key start switch and disconnect switch to the ON position.

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 - Diagnostic code remains active.

Repair : A charging system component may be faulty. Check the charging system. Special Instruction, REHS0354, "Charging System Troubleshooting" for more information.

Proceed to Test Step 4. 
3. Check The Charging System At Low Idle

A. Turn key start switch and disconnect switch to the ON position.

B. Clear all active diagnostic codes.

C. Start the engine. Run the engine at LOW idle.

D. Enter the diagnostic menu on the monitor.

E. Observe status of diagnostic code. 

Diagnostic code is no longer active. 
OK - The diagnostic code is no longer active.

Proceed to Test Step 4.

NOT OK - The diagnostic code is active. The charging system is not charging at the proper output.

Repair : A charging system component may be faulty. Check the charging system. Special Instruction, REHS0354, "Charging System Troubleshooting" for more information.

Proceed to Test Step 4. 
4. Check If The Diagnostic Code Remains

A. Reconnect all harness connectors. Return machine to normal operating condition.

B. Turn the key start switch and the disconnect switch to the ON position.

C. Clear all diagnostic codes.

D. Operate the machine.

E. Stop the machine and engage the safety lock lever.

F. Check if the diagnostic code is active. 

The diagnostic code is no longer present. 
OK - The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation.

STOP

NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement.

Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time.

Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced.

STOP 

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