CIRCUIT BREAKER GP 2704658 - Caterpillar

Note: This procedure checks for an open circuit or for a short circuit in the Cat Data Link. If you are experiencing problems with communications between the Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM), refer to the troubleshooting without a diagnostic code procedure Troubleshooting, "Electronic Service Tool Will Not Communicate with ECM" before you use this procedure.The Cat Data Link is the standard data link that is used by the ECM to communicate with Cat ET. The ECM communicates with Cat ET in order to share status information and diagnostic information. Cat ET can also be used to configure the ECM parameters. This information will not be available if communication fails between the ECM and Cat ET.
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Schematic for the Cat Data Link
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the battery isolator switch to the OFF position.
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Location of the J1/P1 ECM connectors (typical left side engine view)
Thoroughly inspect the J1/P1 ECM connectors. Also, thoroughly inspect the service tool connector. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
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P1 terminals that are associated with the Cat Data Link
(P1-8) Cat Data Link +
(P1-9) Cat Data Link −
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Terminals at the service tool connector that are associated with the Cat Data Link
(D) Cat Data Link +
(E) Cat Data Link −
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the Cat Data Link.
Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. Expected Result:All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and the connectors appear to be OK. Proceed to Test Step 2.
Not OK - The connectors and/or the wiring are not OK.Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the original problem is resolved.STOPTest Step 2. Check the Data Link for a Short Circuit
Disconnect the J1 connector.
Disconnect Cat ET from the service tool connector.
Measure the resistance between the points that are listed in Table 1. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.
Table 1
Resistance Measurements for the Cat Data Link
Connector and Terminal Terminal
P1-8 (Cat Data Link +) All of the other terminals on the P1 connector
Ground stud
P1-9 (Cat Data Link -) All of the other terminals on the P1 connector
Ground stud Expected Result:Each check of the resistance indicates an open circuit.Results:
OK - Each check of the resistance indicates an open circuit. The data link is not shorted to another wire that is in the harness. Proceed to Test Step 3.
Not OK - At least one check of the resistance does not