Electrical Power Supply - Test
Use this procedure to troubleshoot a problem with the power to the engine Electronic Control Module (ECM) and/or the In Cylinder Pressure Sensor (ICPS) ECM. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.
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J1939 Code and Description | CDL Code and Description | Comments |
---|---|---|
168-3
Battery Potential / Power Input #1 : Voltage Above Normal |
168-3
Electrical System Voltage : Voltage Above Normal |
The battery supply voltage is less than 18 VDC on 24 VDC systems for 0.5 seconds or the battery supply voltage is less than 9 VDC on 12 VDC systems for 0.5 second to the engine Electronic Control Module (ECM) and/or the In Cylinder Pressure Sensor (ICPS) ECM.
The engine ECM or ICPS ECM has been powered for 3 seconds. The engine is running for at least 3 seconds. |
168-4
Battery Potential / Power Input #1 : Voltage Below Normal |
168-4
Electrical System Voltage : Voltage Below Normal |
The 24 VDC voltage falls below 18 VDC for .5 seconds.
The 24 VDC voltage must return above 18.2 VDC for 3 seconds in order for the diagnostic to reset. The engine is running for at least 3 seconds. |
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Troubleshooting Test Steps | Values | Results |
---|---|---|
1. Check for Codes A. Connect Cat® Electronic Technician (ET) to the service tool connector. B. Determine if a code is active or logged on either the engine Electronic Control Module (ECM) or the In Cylinder Pressure Sensor (ICPS) ECM. |
Codes |
Result: A -3 code is active or logged. Proceed to Test Step 2. Result: A -4 code is active or logged. Proceed to Test Step 3. |
2. Check the Charging Circuit |
Charging Circuit |
Result: The charging system is OK. Proceed to Test Step 3. Result: The charging system is NOT OK. Repair: There is a problem with the charging system. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting" for additional information. Verify that the repair eliminated the problem. |
3. Inspect the Batteries A. Charge the batteries, if necessary. Refer to Special Instruction, SEHS7633, "Battery Test Procedure" for additional information. B. Load-test the batteries. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8 V and 12 V Lead Acid Batteries" for additional information. |
Batteries |
Result: The batteries pass the load test. The measured voltage is between 11.5 VDC and 13.5 VDC for a 12 V system. The measured voltage is between 23.0 VDC and 27.0 VDC for a 24 V system. Repair: Verify that the "System Operating Voltage Configuration" is correctly configured in the Engine ECM configuration parameters. Verify that the repair eliminated the problem. Result: The battery voltage is low or the battery did not pass the load test. Repair: Repair or replace the batteries. Verify that the repair eliminated the problem. |
If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).
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