The CAT Data Link is used for communication between electronic modules. The CAT Data Link is used to communicate information from the engine's Electronic Control Module (ECM) to other electronic systems. The CAT Data Link is used for programming and troubleshooting the ECM.
The ECM communicates with the Caterpillar Electronic Technician (ET) in order to share status information and diagnostic information. The Cat ET can also be used to configure the ECM parameters. This information will not be available if communication fails between the ECM and the Cat ET.
The ECM communicates with the electronic dash displays in order to communicate the engine's operating status. The ECM communicates with other control modules on the machine.
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| Illustration 1 | g00918459 |
Typical modules (if applicable) | |
Test Step 1. Check for Connector Damage
- Turn the keyswitch to the OFF position.
- Turn the breaker for the engine ECM to the OFF position.
- Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
- 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 ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).
- Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).
- Check the harness and the wiring for abrasion and for pinch points.
Expected Result:
The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.
Results:
- OK - The connectors and wiring are free of any problems. Proceed to test step 2.
- Not OK - The connectors and/or wiring need repair.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
Stop.
Test Step 2. Check for Shorts in the Harness
- Disconnect ECM connector J1/P1 at the engine ECM.
- Disconnect all control modules from the CAT Data Link.
- Disconnect the Cat ET from the service tool connector J42.
- Measure the resistance from P1-3 to P1-9.
- Measure the resistance from P1-9 to the chassis ground.
- Measure the resistance from P1-3 to the chassis ground.
Expected Result:
The resistance should be greater than 20,000 Ohms for each measurement.
Results:
- OK - The resistance is greater than 20,000 Ohms for each measurement. Proceed to test step 3.
- Not OK - The resistance is less than 20,000 Ohms for one or more measurements. There is a short circuit in the harness or connectors.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
Stop.
Test Step 3. Check the Resistance through the Harness.
- Use a suitable piece of wire to create a short circuit at the cab service tool connector J42. Short J42-D and J42-E together.
- Measure the resistance between P1-9 and P1-3.
- Measure the resistance at the connectors of the other control modules.
Expected Result:
The resistance should be less than 10 Ohms for each measurement.
Results:
- OK - The resistance is less than 10 Ohms for each measurement. The CAT Data Link is OK.
Repair: If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".
Stop.
- Not OK - The resistance is greater than 10 Ohms for one or more of the measurements. There is an open circuit in the harness or connectors.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
Stop.