CONNECTOR 0043099 - Caterpillar

This diagnostic code is recorded when the ECM reads the electrical system voltage that is at contact J1-1 as being below normal range (less than 18 volts for two seconds).The possible causes of this diagnostic code are listed:
A charging system component has failed.
The wire harness has failed.
The ECM has failed. This is unlikely.This diagnostic code may cause the outputs of the ECM to operate incorrectly.Ensure that CID 0168 FMI F01 is on hold. The "SERV CODE" indicator is illuminated.Test Step 1. CHECK THE BATTERY VOLTAGE.
Run the engine at high idle.
Measure the voltage at the battery posts. Expected Result:The voltage measures battery voltage.Results:
YES - The voltage is greater than 18 DCV. This should not cause the diagnostic code. Proceed to Test Step 2.
NO - The voltage is less than 18 DCV. The charging system is not correct. Repair: Check the charging system. See Special Instruction, REHS0354, "Charging System Troubleshooting". STOPTest Step 2. CHECK THE SYSTEM VOLTAGE
Turn the disconnect switch and the key start switch to the OFF position.
Disconnect the machine harness from the ECM.
Turn the disconnect switch and the key start switch to the ON position.
Run the machine at high idle.
At machine harness connector J1 for the ECM, measure the voltage between contact J1-1 and contact J1-2. Expected Result:The voltage measures battery voltage.Results:
YES - The voltage is greater 18 DCV. This should not cause the diagnostic code. Repair: Verify that the diagnostic code is still present. If the cause of the diagnostic code is not found, replace the ECM. See Testing And Adjusting, "Electronic Control Module (ECM) - Replace".STOP
NO - The voltage is less than 18 DCV. The machine harness has failed. Repair: Check the +battery circuit and the ground circuit in the machine harness. Inspect the connectors and clean the connectors. Repair the machine harness or replace the machine harness. STOP