COVER 7N2057 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the Cat Data Link if a problem with the wiring is suspected. The Cat Data Link is used for communication between electronic modules. The Cat Data Link is used to communicate information from the Electronic Control Module (ECM) to other electronic systems. The Cat Data Link is used for programming and troubleshooting the ECM.The ECM communicates with Caterpillar Electronic Technician (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.
Illustration 1 g01227891
Typical schematic
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove power from the ECM.
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the connectors to other modules on the Cat Data Link. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Illustration 2 g01227893
P1 ECM connector
(P1-8) Cat Data Link +
(P1-9) Cat Data Link −
Illustration 3 g01234034
Terminal locations at the customer connector
(Terminal 6) Cat Data Link −
(Terminal 7) Cat Data Link +
Illustration 4 g01234041
Terminal locations at the service tool connector
(Terminal D) Cat Data Link +
(Terminal E) Cat Data Link −
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw for each ECM connector for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points. Expected Result:All of the connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring are not OK.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Check for Shorts in the Harness
Disconnect ECM connector J1/P1 at the engine ECM.
Disconnect any control modules from the Cat Data Link.
Disconnect Cat ET from the service tool connector.
Measure the resistance from P1-8 to every terminal on ECM connectors P1 and P2.
Measure the resistance from P1-8 to the chassis ground.
Measure the resistance from P1-9 to every terminal on ECM connectors P1 and P2.
Measure the resistance from P1-9 to the chassis ground.