Use this procedure to troubleshoot the electrical system if a problem is suspected with the Cat Data Link or if another procedure has sent you here.
Note: This procedure checks for an open circuit or for a short circuit in the Cat Data Link. If you are experiencing problems with communications between Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM), refer to Troubleshooting, "Electronic Service Tool Does Not Communicate" before you use this procedure.
The Cat Data Link is the standard data link that is used by the ECM to communicate with Cat 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.
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| Illustration 1 | g01421618 |
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Typical schematic for the Cat Data Link | |
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The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere. |
Test Step 1. Inspect the Electrical Connectors and the Wiring
- Remove electrical power from the ECM.
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Illustration 2 g01385856 Location of the ECM connectors for the Cat Data Link (typical left side engine view)
(1) J1/P1 ECM connectors - Thoroughly inspect connectors (1) and (2). Refer to Troubleshooting, "Electrical Connectors - Inspect".
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Illustration 3 g01312112 Terminal locations at the P1 ECM connector for the Cat Data Link
(P1-8) Cat Data Link +
(P1-9) Cat Data Link −Show/hide table
Illustration 4 g01388995 Terminals at the customer connector that are associated with the Cat Data Link
(7) Cat Data Link +
(6) Cat Data Link −Show/hide table
Illustration 5 g01388996 Terminals at the service tool connector that are associated with the Cat Data Link
(Terminal G) Cat Data Link +
(Terminal F) Cat Data Link − - Perform a
45 N (10 lb) pull test on each of the wires that are associated with the Cat Data Link. - Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
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 connectors appear to be OK. Proceed to Test Step 2.
- Not OK - The connectors and/or the wiring are not OK.
Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the original problem is resolved.
STOP
Test Step 2. Check for a Short Circuit
- Disconnect the P1 ECM connector.
- Disconnect Cat ET from the service tool connector.
- Disconnect any other control modules from the Cat Data Link. Refer to the electrical schematic in order to identify other control modules on the Cat Data Link.
- Measure the resistance between the points that are listed in Table 1. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.
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Table 1 Resistance Measurements for the Cat Data Link Connector and Terminal Terminal P1-8 (Cat Data Link +) All of the other terminals on the P1 connector Ground stud P1-9 (Cat Data Link -) All of the other terminals on the P1 connector Ground stud
Expected Result:
Each check of the resistance indicates an open circuit.
Results:
- OK - Each check of the resistance indicates an open circuit. Proceed to Test Step 3.
- Not OK - At least one check of the resistance does not indicate an open circuit. There is a short circuit in the harness or in a connector.
Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Verify that the original problem is resolved.
STOP
Test Step 3. Check for an Open Circuit
- Fabricate a jumper wire. Use the jumper wire in order to create a short circuit between terminals D (Cat Data Link +) and terminal E (Cat Data Link −) on the service tool connector.
- Measure the resistance between P1-8 (Cat Data Link +) and P1-9 (Cat Data Link −).
- Measure the resistance between the terminals at the connector for each control module that was connected to the Cat Data Link.
- Remove the jumper wire from the service tool connector.
Expected Result:
Each check of the resistance indicates a short circuit.
Results:
- OK - Each check of the resistance indicates a short circuit.
Repair: There is a problem with the ECM. Perform the following procedure:
- Temporarily connect a test ECM.
Refer to Troubleshooting, "ECM - Replace".
- Recheck the circuit in order to ensure that the original problem has been resolved.
If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.
If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.
STOP
- Temporarily connect a test ECM.
- Not OK - At least one check of the resistance does not indicate a short circuit. There is an open circuit or excessive resistance in the harness. There may be a problem with a connector.
Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Verify that the original problem is resolved.
STOP