This diagnostic trouble code is recorded when the ECU detects a battery voltage of less than 9 VDC.
The possible causes of this diagnostic trouble code are listed:
- Failure in machine wiring harness
- Charging system component failure
- The ECU has failed. This is unlikely.
Determine if a battery charger is being used on the vehicle. Disconnect the charger if one is used. Recheck for the diagnostic trouble code. Check the charging system if the diagnostic trouble code is still active.
Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear these diagnostic trouble codes when the original diagnostic trouble code has been corrected. Ensure that the diagnostic trouble code of SPN 168 FMI 4 is active before performing this procedure.
Test Step 1. Check the Battery Voltage at the J1 Connector
| 12 VDC System | 24 VDC System | ||
|---|---|---|---|
| Low Range | High Range | Low Range | High Range |
| 12 ± 0.5 VDC | 13 ± 0.5 VDC | 24 ± 0.5 VDC | 28 ± 0.5 VDC |
Determine if there are other electrical problems. If there are other electrical problems, there is a problem with the battery or with the wiring between the battery and the overcurrent protection devices.
Continue with this procedure if there are no other indications of electrical problems.
- Do not turn off the engine.
- Use Cat Electronic Technician (ET) to view the value of the "ECM Battery Voltage" parameter.
Expected Result:
The voltage is less than 9.0 VDC.
Results:
- The voltage is less than 9.0 VDC - Proceed to Test Step 2.
- The voltage is greater than 9.0 VDC. - Cat ET indicates a "ECM Battery Voltage" that is greater than 9.0 VDC. However, there is an active SPN 168 FMI 4 code.
Repair: Replace the ECM. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace". Verify that the problem is resolved.
STOP
Test Step 2. Check the Voltage at the Battery
Measure the voltage at the battery terminals.
Expected Result:
The voltage is less than 9.0 VDC.
Results:
- OK - The voltage at the battery terminals is less than 9.0 VDC. There is a problem with the battery or with the charging system.
Repair: Load test the battery. Replace the battery, if necessary. Test the charging system. Refer to Systems Operation/Testing and Adjusting, "Charging System - Test" in the manual for the engine that is being serviced.
STOP
- Not OK - The voltage at the battery terminals is greater than 9.0 VDC. However, the voltage at the P1 terminals is less than 9.0 VDC.
Repair: The problem is in the vehicle wiring. The voltage drop can be caused by wiring or by a component. Identify the cause of the voltage drop. Repair the problem, when possible. Replace parts, if necessary. Send the vehicle to the OEM dealer for repair, if necessary. Verify that the problem is resolved.
STOP