GEAR AS-SUN 3134674 - Caterpillar

The CAT Data Link is a two wire electrical connection that is used for communication between electronic modules such as the engine Electronic Control Module (ECM), the machine control module, electronic transmission controls, electronic dash displays, and ET.The ECM communicates with electronic dash displays in order to share engine information and electronic system diagnostics.The ECM communicates with ET in order to share status information and diagnostic information. ET can also be used to configure the ECM parameters. This information will not be available if communication fails between the ECM and ET.
Illustration 1 g00738597
Schematic
Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect ECM connector J1/P1 and all other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. Note: Refer to the Electrical System Schematic for further information about the machine wiring.Expected Result:All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 2. Check for Shorts in the Harness
Illustration 2 g00738644
ECM connector P1
Disconnect ECM connector J1/P1.
Disconnect all modules from the CAT Data Link.
Disconnect ET from the service tool connector.
Measure the resistance between P1:3 (CAT Data Link −) and P1:9 (Cat Data Link +).
Measure the resistance between P1:9 (Cat Data Link +) and chassis ground.
Measure the resistance between P1:3 (CAT Data Link −) and chassis ground. Expected Result:The resistance should be greater than 20,000 Ohms for each measurement.Results:
OK - Proceed to Test Step 3.
Not OK - There is a short circuit in the harness or connectors.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 3. Check Resistance Through the Harness
Illustration 3 g00738644
Use a suitable piece of wire to short J42:D (CAT Data Link +) and J42:E (CAT Data Link −) at the service tool connector.
Measure the resistance between P1:9 (CAT Data Link +) and P1:3 (CAT Data Link −).
Measure the resistance across the CAT Data Link at the other modules. Expected Result:The resistance should be less than 10 Ohms for each measurement.Results:
OK - The CAT Data Link is OK.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.STOP
Not OK - There is an open circuit or excessive resistance in the harness or connectors.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOP