LAMP AS 3044682 - Caterpillar

Use this procedure to troubleshoot any suspect problems with the Cat Data Link.Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:
296-09 Unable to communicate with Transmission ECM
296-12 Transmission ECM Failed
596-09 Unable to communicate with Implement ECM
596-12 Wrong Respnse from Implement ECM
1639-09 Machine Security System Module not communicating on linkNote: 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
Remove the electrical power from the ECM.
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Engine view (typical example)
(1) J1/P1 connectors
Thoroughly inspect connector (1). 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 that are associated with the "Cat Data Link" on the machine connector
(P1-26) Cat Data Link +
(P1-27) 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".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 for a Short Circuit
Disconnect the P1 ECM connector.
Disconnect Cat ET from the service tool connector.
Disconnect any other control modules from the "Cat Data Link".
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