SHROUD AS 3916409 - Caterpillar

Which Generate This Code:The diagnostic circuit of the Power Train/Chassis Electronic Control Module (ECM) identifies a system voltage that is below 18 DCV.The possible causes of this diagnostic code are listed:
The system voltage remains low for an extended time after the engine is started.
There is a connection with high impedance between the battery and the ECM.
There is a connection with high impedance between the ECM and system ground.
One set of batteries is disconnected with the key in the ON position. Also, the engine must not be running.Note: Ensure that the diagnostic code is active.Test Step 1. CHECK THE BATTERY VOLTAGE
Start the engine and operate the engine at high idle for several minutes.
Check the system voltage at the machine batteries.Expected Result:Battery voltage is 18 DCV to 35 DCV.Results:
OK - Battery voltage is 18 DCV to 35 DCV. The battery voltage is correct. Proceed to Test Step 2.
NOT OK - Battery voltage is below 18 DCV or above 35 DCV.Repair: The charging system is not operating correctly. Check the charging system. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting". Stop.Test Step 2. CHECK THE SYSTEM VOLTAGE AT THE ECM
The engine must be running at high idle.
Measure the system voltage between contact J1-1 (wire 164-WH) or contact J1-31 or J1-39 and contacts J1-13 or J1-23 (wire 202-BK). Measure the system voltage at the contacts of the harness connector.Expected Result:The voltage is above 18 DCV.Results:
OK - The voltage is above 18 DCV. Proceed to Test Step 3.
NOT OK - Voltage is below 18 DCV. The machine harness has failed.Repair: Repair the machine harness or replace the machine harness. Stop.Test Step 3. CHECK IF THE DIAGNOSTIC CODE REMAINS
Inspect the contacts of the harness connectors and clean the harness connectors.
Reconnect all the harness connectors.
Turn the battery disconnect switch and the key start switch to the ON position.
Operate the machine.
Check the status of the CID 0168 FMI 01. Expected Result:The CID 0168 FMI 01 is active. Results:
YES - The CID 0168 FMI 01 is active. The diagnostic code has not been corrected. The ECM may have failed.Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Refer to Systems operation, Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace" for the machine that is being serviced. Stop.
NO - The CID 0168 FMI 01 is not active. The diagnostic code does not exist at this time. Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation. Stop.