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 Caterpillar Electronic Technician (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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| Illustration 1 | g00837184 |
Schematic | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the keyswitch to the OFF/RESET position.
- Thoroughly inspect ECM connector J1/P1 and machine connector J3/P3. 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 are completely inserted and coupled. The harness and wiring are of corrosion, of abrasion, and of pinch points.
Results:
- OK - Proceed to Test Step 2.
- Not OK - There is a problem with the wiring and/or with a connector.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
STOP
Test Step 2. Check for Shorts in the Harness
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| Illustration 2 | g00715687 |
ECM connector P1 | |
- Disconnect ECM connector J1/P1.
- Disconnect all modules from the Cat Data Link.
- Disconnect Cat 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 is 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.
STOP
Test Step 3. Check Resistance through the Harness
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| Illustration 3 | g00715687 |
ECM connector P1 | |
- 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 is 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 in the connectors.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
STOP