C7.1 Marine Engine Caterpillar

Use this procedure if a fault is suspected in the CAN data link. This procedure also covers the following diagnostic codes:

Table 1

Diagnostic Trouble Codes for the CAN Data Link
J1939 Code	Description	Notes
639-9	J1939 Network #1 : Abnormal Update Rate	Another controller has incorrectly stopped transmitting a J1939 speed request (TSC1) or another controller has incorrectly started transmitting a J1939 speed request. The ECM will log the diagnostic code. The engine will not start.
639-14	J1939 Network #1 : Special Instruction	Another controller has incorrectly stopped transmitting a signal on the CAN data link.

The 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 transferred 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 in order 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 the 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	g06081626
Typical example of the schematic for the CAN data link (1) 70 Way Connector

Illustration 2	g06081623
70 Way Connector

Table 2

Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Turn the keyswitch to the OFF position. B. Inspect the connectors in the circuit for the CAN data link. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 30 N (6.7 lb) pull test on each of the wires that are associated with the CAN data link. D. Check all of the wiring associated with the CAN data link for abrasions and pinch points.	Damaged wire or connector	Result: A damaged wire or damaged connector was found. Repair the damaged wire or the damaged connector. Use the electronic service tool to clear all logged diagnostic codes. Verify that the repair eliminates the fault. Result: A damaged wire or damaged connector was not found. Proceed to Test Step 2.
2. Check the Data Link Terminating Resistance A. Disconnect the P1 connector from the ECM. B. Measure the resistance between the J2: 23 and J2 31.	Between 50 Ohms and 70 Ohms	Result: The resistance is less than 50 Ohms - there is a short circuit in the harness. 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 correctly connected. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The resistance is between 110 and 130 Ohms - one of the terminating resistors may have failed. Locate the two terminating resistors and remove the two terminating resistors from the harness. The terminating resistors may be located in other ECMs on the data link. Refer to the Electrical Schematic. Measure the resistance of the two terminating resistors. If one of the terminating resistors is incorrect, replace the faulty terminating resistor. If the two terminating resistors are between 50 and 70 Ohms each, proceed to Test Step 4. Result: The resistance is greater than 150 Ohms. Proceed to Test Step 3. Result: 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.
3. Check the Data Link Wiring A. Disconnect each of the connectors that connect other devices on the data link. B. Use a multimeter to measure the resistance between J2:23 and each of the CAN+ pins for other devices on the CAN data link. C. Use a multimeter to measure the resistance between J2:23 and pin F on the diagnostic connector. D. Use a multimeter to measure the resistance between J2:31 and each of the CAN- pins for other devices on the CAN data link. E. Use a multimeter in order to measure the resistance between J2:31 and pin G on the diagnostic connector.	Less than 5 Ohms	Result: At least one of the resistance measurements is greater than 5 Ohms - there is an open circuit or high resistance in the wiring. Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all seals are correctly in place and ensure that the connectors are correctly connected. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair has eliminated the fault. Result: All measured resistances are less than 2 Ohms. Proceed to Test Step 4
4. Check the Other Devices on the CAN Data Link A. Use the appropriate service tools in order to diagnose other devices on the data link.	Other devices are OK	Result: At least one of the other devices is not operating correctly. Use the appropriate service tools in order to repair other devices on the data link. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The other devices are operating correctly. Contact the Dealer Solution Network (DSN).

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).