RING (Top) 7S8378 - Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engines Electronic Control Module (ECM). Use this procedure if any of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
J1939 Code and Description Conditions which Generate this Code System Response
168-3 Battery Potential / Power Input #1 : Voltage Above Normal Electrical System Voltage : Voltage Above Normal The code is logged.
168-4 Battery Potential / Power Input #1 : Voltage Below Normal Electrical System Voltage : Voltage Below Normal The code is logged. The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).
Illustration 1 g02967337
Schematic
Illustration 2 g03034832
EL-C3 connector & EL-C8 connector
(22) + Batt sec.
(23) + Batt sec.
(25) + Batt prim.
(26) + Batt prim. & -Batt sec.
(27) - Batt sec.
(28) - Batt prim.
(29) - Batt prim.
Illustration 3 g03034882
ER-C62 connector & ER-C63 connector
(2) + Batt sec.
(3) + Batt sec. & +Batt prim.
(4) + Batt prim.
(5) + Batt prim.
(6) + Batt prim. & -Batt sec.
(7) - Batt sec.
Table 2
1. Inspect the Electrical Connectors and the Wiring
A. Turn the main disconnect switch to the OFF position.
B. Thoroughly inspect the ECM connectors. Also, thoroughly inspect the other connectors for the electrical power circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the proper procedure for inspecting the connectors and the wiring.
Electrical connectors
Results: The connectors and wiring appear to be OK.
Proceed to Test Step 2.
Results: There is a problem in the connectors and/or wiring.
Repair The connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled.
Verify that the repair eliminated the problem.
2. Check the Voltage to the ECM
A. Disconnect the ECM connector J1/P1.
B. Restore the electrical power to the ECM.
C. Measure the voltage at the ECM. Measure the voltage between P1-53 and P1-65. Measure the voltage between P1-52 and P1-63.
ECM voltage
Result: The voltage is 24 3 VDC.
The ECM is receiving the correct voltage. The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
Result: The voltage is less than 24 3 VDC.
The wiring or components between the battery and the ECM may be preventing the voltage from reaching the ECM.
Proceed to Test Step 3
3. Check the Charging Circuit
A. Turn the main disconnect switch to the OFF position.
A. Check the charging circuit.
Charging circuit
Result: The charging system is OK.
Proceed to Test Step 4.
Result: The charging system is not OK.
There is a problem with the charging system. Make the necessary repairs. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting".
Verify that the repair eliminated the problem.
4. Load Test the Battery
A. Load-test the battery. Refer to Systems Operation and Testing and Adjusting, "Battery - Test"
Load test
Result: The battery voltage is low or the battery did not pass the load test.
Repair: Recharge or replace the faulty batteries.
Verify that the repair eliminated the problem.
Result: The batteries pass the load test. The measured voltage is between 11.5 VDC