EDGE-CUTTING 9W8620 - Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engines Electronic Control Module (ECM). Also, use this procedure if one of the following diagnostic codes 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 g03658891
Schematic for the electrical power supply (typical example).
Illustration 2 g03321350
Location of the J1/P1 and the J2/P2 ECM connectors (typical engine view). (1) J1/P1 ECM connector (2) J2/P2 ECM connector
Illustration 3 g03658881
P2 ECM connector (P1-43) + Starter enable relay (P1-51) Return
Illustration 4 g01206554
P1 ECM connector (P1-48) +Battery (P1-52) +Battery (P1-53) +Battery (P1-55) +Battery (P1-57) +Battery (P1-61) −Battery (P1-63) −Battery (P1-65) −Battery (P1-67) −Battery (P1-69) −Battery (P1-70) Keyswitch
Illustration 5 g03678643
Engine interface connector (Terminal AC) Auxiliary 1 + Battery (Terminal AH) Auxiliary 1 + Battery (Terminal AJ) Auxiliary 2 + Battery (Terminal AK) Emergency Stop (Terminal AL) Auxiliary 2 + Battery (Terminal AM) Emergency Stop 2 (Terminal AT) Auxiliary 1 − Battery (Terminal AV) Auxiliary 1 − Battery (Terminal AX) Auxiliary 2 − Battery (Terminal AZ) Auxiliary 2 − Battery (Terminal BC) Keyswitch
Illustration 6 g03677160
Power interface connector 1 (37 pin connector) (Terminal 14) Auxiliary 2 + Battery (Terminal 15) Auxiliary 2 + Battery (Terminal 16) Auxiliary 2 − Battery (Terminal 17) Auxiliary 2 − Battery (Terminal 35) Emergency Stop 2
Illustration 7 g03677162
Power interface connector 2 (25 pin connector) (Terminal 2) + Battery (Terminal 3) + Battery (Terminal 4) + Battery (Terminal 5) − Battery (Terminal 6) − Battery (Terminal 8) − Battery (Terminal 14) Auxiliary 1 + Battery (Terminal 15) Auxiliary 1 + Battery (Terminal 16) Auxiliary 1 − Battery (Terminal 17) Auxiliary 1 − Battery (Terminal 21) Emergency Stop
Illustration 8 g03323077
Terminal locations for the ECM relay and the connector (typical example) (3) ECM relay (Terminal 1) +Battery (Terminal 2) Relay ground (Terminal 3) Electrical power to the ECM (Terminal 5) Relay control
Table 2
1. Inspect Electrical Connectors and Wiring
A. Turn the main disconnect switch to the OFF position.
B. Thoroughly inspect the ECM connectors J1/P1. Inspect all of the other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a
45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
D. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
E. Check the harness and the wiring for abrasion and for pinch points.
   
Connectors    
Result: The connectors and wiring appear to be OK.
Proceed to Test Step 2.
Result: The connectors and/or wiring are