BRACKET 5J0120 - Caterpillar

Use this procedure if a fault is suspected in the CAN data link. Also, use this procedure if the following diagnostic code is active:
Table 1
Diagnostic Trouble Codes for the 5 VDC Sensor Supply Circuit
J1939 Code Description Notes
639-14 J1939 Network #1 : Special Instruction The Electronic Control Module (ECM) detects a fault on the CAN data link for at least 0.1 seconds.
The warning lamp will flash. The engine will be derated. The following background information is related to this procedure:The CAN data links are also known as J1939 data links. A data link is an industry standard for sending data between different devices in the same application.High speed data is transferred via the data links. The data links cannot be accurately tested without complicated equipment. The data links require a resistance of 60 Ohms between the two wires to transmit the data correctly. This resistance is made up of two 120 Ohm resistors. The two resistors are known as "Terminating Resistors". The terminating resistors should be at opposite ends of a data link circuit. If this resistance is not present, then the data will be intermittent or unreadable.Note: The wiring for a J1939 data link is a shielded twisted pair cable. If the wiring is damaged, the replacement type must be shielded twisted pair cable.
Illustration 1 g03237156
Typical example of the schematic for the CAN 0 data link
Illustration 2 g03239957
Typical view of the pin locations on the P1 connector
(16) CAN 0+
(36) CAN 0- Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect the connectors in the circuit for the CAN data link. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the CAN data link.
Check the harness for abrasion and pinch points from the keyswitch to the Electronic Control Module (ECM). Expected Result:All connectors, pins, and sockets are correctly connected. The harness should be free of corrosion, abrasion and/or pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Perform the following repair:Repair the connectors and/or the wiring, or replace the connectors and/or the wiring. Ensure that all of the seals are correctly in place and ensure that the connectors are