CUP-SPHERICAL 3T1377 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the following data links:
Cat Data Link
CAN data link (J1939)
ATA data linkIf the Caterpillar Electronic Technician (ET) will not communicate with the Electronic Control Module (ECM), refer to Troubleshooting, "Electronic Service Tool Does Not Communicate" before you begin this procedure. The procedure verifies that electrical power is being supplied to the ECM and to the service tool connector.Background InformationCat ET - Cat ET is the standard data link that communicates with the ECM and other modules.CAN Data Link (J1939) - The CAN data link communicates engine information to other modules.ATA Data Link - The ATA data link communicates ECM information to the electronic service tools.
Illustration 1 g01431680
SchematicTest Step 1. Inspect Electrical Connectors And Wiring
Remove electrical power from the ECM.
Illustration 2 g01139425
ECM (1) J1/P1 connectors (2) J2/P2 connectors
Thoroughly inspect connectors (1) and (2). Inspect the harness and all of the other connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01432162
P1 ECM connector (P1-1) ATA data link (-) (P1-7) ATA data link (+) (P1-3) Cat Data Link (-) (P1-9) Cat Data Link (+) (P1-39) CAN data link (-) (P1-33) CAN data link (+)
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the ATA data link.
Check the allen head screw on the ECM connectors and the customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque value.
Check the wiring harnesses for abrasion, for corrosion, and for pinch points.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 wiring appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem in the wiring harness.Repair: Complete the necessary repairs and/or replace parts, if necessary. Refer to Troubleshooting, "Electrical Connectors - Inspect".STOPTest Step 2. Check the Wiring for the Data Links for a Short Circuit
Remove electrical power from the ECM.
Disconnect the ECM connector J1/P1 and J2/P2 at the ECM.
Disconnect any control modules from the data links.
Disconnect Cat ET from the service tool connector.
Measure the resistance between the following terminals:
P1-7 (ATA data link +) and every terminal on ECM connectors P1 and P2
P1-7 (ATA data link +) and chassis ground
P1-1 (ATA data link -) and every terminal on ECM connectors P1 and P2
P1-1 (ATA data link -) and chassis ground
P1-33 (CAN data link +) and every terminal on ECM connectors P1 and P2
P1-33 (CAN data link +) and chassis ground
P1-39 (CAN data link -) and every terminal on ECM connectors P1 and P2
P1-39 (CAN data link -) and chassis ground
P1-9 (Cat Data Link +) and every terminal on ECM connectors P1 and P2
P1-9 (Cat Data Link +) and chassis ground
P1-3 (Cat Data Link -) and every terminal on ECM connectors P1 and P2
P1-3 (Cat Data Link -) and chassis groundExpected Result:Each measurement indicates an open circuit.Results:
OK - Each measurement indicates an open circuit. The wiring