BREAKER, CIRCUIT - 40 AMP 3-299 - Caterpillar

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Schematic
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P1 ECM connector
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Service Tool ConnectorTest Step 1. Test Communication of the CAT Data Link
Turn the keyswitch to the OFF/RESET position.
Connect Cat ET to the service tool connector.
Turn the keyswitch to the ON position.
Select the engine ECM from the "ECM Selector" screen on Cat ET.Results:
OK - The CAT Data Link is functioning properly. Proceed to Test Step 2.
Not OK - The CAT Data Link is not functioning properly.Repair: Proceed to Troubleshooting, "Electronic Service Tool Will Not Communicate with ECM". Stop.Test Step 2. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect J1/P1 ECM connector 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 engine 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 3.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 3. Check the Resistance of the ATA Data Link
Turn the keyswitch to the OFF position.
Disconnect the J1/P1 ECM connector.
Measure the resistance between P1:1 (ATA Data Link (-)) and P1:7 (ATA Data Link (+)).Note: Resistance should be greater than 20,000 ohms.
Install a jumper wire with Deutsch sockets on each end between J42:J and J42:H.
Measure the resistance between P1:1 (ATA Data Link (-)) and P1:7 (ATA Data Link (+)).Note: Resistance should be less than 10 ohms.
Remove the jumper wire and reconnect the J1/P1 ECM connector.Expected Result:The resistance should be greater than 20,000 ohms, when the jumper wire is removed. Resistance should be less than 10 ohms when the jumper wire is installed.Results:
OK - There does not appear to be a problem with the ATA data link at this time. Proceed to Test Step 4.
Not OK - There is either an open circuit or a short circuit in the ATA data link.Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 4. Change Components
Use the same components and attempt to connect to another Caterpillar electronic engine.
If another engine is not available, find a different communication adapter and find a different set of cables. Ensure that the communication adapter and cables are a complete set. Connect Cat ET to the service tool connector with the new communication adapter and cables.
Turn the ignition key switch to the ON position. Determine if Cat ET communicates correctly with the engine.
If changing the communication adapter and cables causes Cat ET to properly communicate, use the following procedure:
Replace the new communication adapter and cables with the old communication adapter and cables by changing one component at a time.
Repower Cat ET after each component is changed. Use this method until you find the faulty component.Results:
Result 1 - The original communication adapter and cables work on another engine. Repair: Cat ET is working properly.Refer toTroubleshooting, "Electrical Connectors - Inspect". Stop.
Result 2 - A different communications adapter and cables work on the original engine. Repair: