Machine ECM
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the system voltage circuit of the machine.
| 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 | g03266701 |
Machine ECM electrical system connections | |
Note: 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, UENR2694 for the complete schematic.
Implement ECM 1
| Implement ECM 1 (MID 432 ) | ||
| DTC | Code Description | System Response |
| 168-3 | Electrical System Voltage : Voltage Above Normal | Numerous machine system failures can be expected when this code is active. |
| 168-4 | Electrical System Voltage : Voltage Below Normal | Numerous machine system failures can be expected when this code is active. |
Possible Causes for an FMI 3 diagnostic code are:
- A charging system component has failed.
- The harness wiring has failed.
- The Machine ECM has failed. A failure of the ECM is unlikely.
The FMI 3 error code will be logged when the system voltage is greater than 16.0 VDC. System electronics may be damaged if the voltage remains high for an extended time.
Possible Causes for an FMI 4 diagnostic code are:
- A charging system component has failed.
- The harness wiring has failed.
- The Machine ECM has failed. A failure of the ECM is unlikely.
The FMI 4 error code will be logged when the system voltage is less than 9.0 VDC.
 | |
| Illustration 2 | g03266736 |
Implement ECM 1 electrical system connections | |
Note: 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, UENR2694 for the complete schematic.
Implement ECM 2
| Implement ECM 2 (MID 433 ) | ||
| DTC | Code Description | System Response |
| 168-3 | Electrical System Voltage : Voltage Above Normal | Numerous machine system failures can be expected when this code is active. |
| 168-4 | Electrical System Voltage : Voltage Below Normal | Numerous machine system failures can be expected when this code is active. |
Possible Causes for an FMI 3 diagnostic code are:
- A charging system component has failed.
- The harness wiring has failed.
- The Machine ECM has failed. A failure of the ECM is unlikely.
The FMI 3 error code will be logged when the system voltage is greater than 16.0 VDC. System electronics may be damaged if the voltage remains high for an extended time.
Possible Causes for an FMI 4 diagnostic code are:
- A charging system component has failed.
- The harness wiring has failed.
- The Machine ECM has failed. A failure of the ECM is unlikely.
The FMI 4 error code will be logged when the system voltage is less than 9.0 VDC.
 | |
| Illustration 3 | g03267799 |
Implement ECM 2 electrical system connections | |
Note: 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, UENR2694 for the complete schematic.
Implement ECM 3
| Implement ECM 3 (MID 434 ) | ||
| DTC | Code Description | System Response |
| 168-3 | Electrical System Voltage : Voltage Above Normal | Numerous machine system failures can be expected when this code is active. |
| 168-4 | Electrical System Voltage : Voltage Below Normal | Numerous machine system failures can be expected when this code is active. |
Possible Causes for an FMI 3 diagnostic code are:
- A charging system component has failed.
- The harness wiring has failed.
- The Machine ECM has failed. A failure of the ECM is unlikely.
The FMI 3 error code will be logged when the system voltage is greater than 16.0 VDC. System electronics may be damaged if the voltage remains high for an extended time.
Possible Causes for an FMI 4 diagnostic code are:
- A charging system component has failed.
- The harness wiring has failed.
- The Machine ECM has failed. A failure of the ECM is unlikely.
The FMI 4 error code will be logged when the system voltage is less than 9.0 VDC.
 | |
| Illustration 4 | g03267800 |
Implement ECM 3 electrical system connections | |
Note: 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, UENR2694 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.
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 1. Identify Active FMI Code Associated With Solenoid Circuit | Code present | FMI 3 diagnostic code, proceed to Test Step 2. FMI 4 diagnostic code, proceed to Test Step 5. FMI 5 diagnostic code, proceed to Test Step 7. |
| Begin Process For DTC 168-3 Troubleshooting HERE | ||
| 2. Check The Charging System A. Turn key start switch and disconnect switch ON. B. Observe the status of the diagnostic code. |
Diagnostic code remains active. |
OK - The diagnostic code remains active. Proceed to Test Step 4. NOT OK - The diagnostic code is no longer active. Proceed to Test Step 3. |
| 3. Check The Charging System A. Start the engine. B. Observe the status of the diagnostic code. |
Diagnostic code is active. |
OK - Diagnostic code is active Repair: The charging system is charging at an excessive voltage. Check the charging system. See Special Instruction, SEHS0354, "Charging System Troubleshooting." Proceed to Test Step 4. NOT OK - Diagnostic code is not active. Repair: There is no problem at this time. Watch for a recurrence. STOP |
| 4. Check The Battery Voltage A. The engine is stopped. At the battery, measure the voltage.. |
The voltage is less than 16.0 VDC |
OK - The voltage is less than 16.0 VDC. Repair: Exit this procedure and perform the diagnostic code procedure again. If the problem persists, the ECM may have failed. Prior to replacing to the ECM, contact the local dealership for possible consultation with Caterpillar. This consultation may greatly effect repair time. See Troubleshooting, "Electronic Control Module (ECM) - Replace" STOP NOT OK - The voltage is not less than 16.0 VDC. Repair: The charging system is charging at an excessive voltage. Check the charging system. See Special Instruction, SEHS0354, "Charging System Troubleshooting" STOP |
| Begin Process For DTC 168-4 Troubleshooting HERE | ||
| 5. Check The Battery Voltage A. Start the machine and run at high idle for several minutes. B. Measure the battery voltage at the battery posts. |
Battery voltage is greater than 9.0 VDC. |
OK - Battery voltage is greater than 9.0 VDC. Battery voltage is correct. Proceed to Test Step 6. NOT OK - Battery voltage is not greater than 9.0 VDC Repair: The charging system is not operating correctly. Check the charging system. See Special Instruction, SEHS0354, "Charging System Troubleshooting" |
| 6. Check The Battery Voltage A. The engine must still be running at high idle. B. With the machine harness remaining connected, prepare to make a voltage measurement at the J1 connector at the ECM with a multimeter probe. C. At the machine harness for the ECM, insert the probe into the back of the J1 connector. Measure the voltage (VDC) between J1-39 and J1-23. |
Voltage is greater than 9.0 VDC. |
OK - Voltage is greater than 9.0 VDC. Battery voltage is correct. Proceed to Test Step 10. NOT OK - Voltage is not greater than 9.0 VDC Repair: The machine harness is not correct. Repair the machine harness or replace the machine harness. |
| Begin Process For DTC 168-5 Troubleshooting HERE | ||
| 7. 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 8. 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 Ω 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. STOP |
| 8. 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 9. 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. STOP |
| 9. Check The Charging System At Low Idle A. Turn key start switch and disconnect switch ON. 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 10. 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. STOP |
| 10. Check If The Diagnostic Code Remains. A. Perform a 45 N (10 lb) pull test on each of the wires associated with the power supply circuit. B. Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened securely. C. Turn key start switch and disconnect switch ON. D. Clear all diagnostic codes. E. Operate the machine. F. Stop machine and engage safety lock lever. G. Check if diagnostic code for the solenoid is active. |
Code for solenoid is NO longer present. |
OK - Diagnostic code does not exist at this time. 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 - Diagnostic trouble code has not been corrected. Recheck the circuit and perform this procedure again. If the diagnostic code has not been corrected after performing the procedure a second time, follow procedure for replacing the ECM. Prior to replacing the ECM, always contact the Technical Communication at your dealership for possible consultation with Caterpillar. This consultation may greatly effect repair time. Follow the steps in Troubleshooting, "Electronic Control Module (ECM) - Replace" if the ECM needs to be replaced. STOP |