ROD AS 4T0406 - Caterpillar

System Operation Description:Use this procedure under the following circumstances:Use this procedure if another procedure has directed you here. Use this procedure if any of the following diagnostic codes are active:
0247-09 SAE J1939 Data Link abnormal update rate
0247-12 SAE J1939 Data Link failureThe following background information is related to this procedure:The CAN Data Link is also known as J1939 Data Link. The data link is an industry standard for sending data between different devices in the same application.High speed data is transfered via the data link. The data link cannot be accurately tested without complicated equipment. The data link requires a resistance of 60 Ohms between the two wires to correctly transmit the data. 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 network. If this resistance is not present, then the data will be intermittent or completely unreadable.Note: The wiring for the J1939 data link is a twisted pair. If the wiring is damaged, the replacement type must be a twisted pair.
Illustration 1 g01619723
Schematic for the CAN data link
Illustration 2 g01458450
Pin locations on the P1 connector
(20) CAN-
(21) CAN+ Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect the harness connector P1/J1 and any other 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. Refer to Illustration 2.
Check the harness for abrasion and pinch points from the keyswitch to the Electronic Control Module (ECM). Expected Result:All connectors, pins and sockets should be completely coupled and/or inserted. 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 completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOPTest Step 2. Check the Data Link Terminating Resistance
Disconnect connector P1 from the ECM.
Measure the resistance between P1:20 and P1:21. Expected Result:The resistance is between 50 and 70 Ohms.Results:
Result 1 - The resistance is between 50 and 70 Ohms. This is the correct resistance. The fault may be in the connection to other devices on the data link. Proceed to Test Step 3.
Result 2 - The resistance is less than 50 Ohms. There is a short circuit in the harness.Repair: Repair the connectors or the harness and/or replace the connectors or the harness.Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOP
Result 3 - The resistance