C280 Marine Engines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power mode relay. Also, use this procedure if the diagnostic code in Table 1 is active.

Table 1

J1939 Code and Description	CDL Code and Description	Comment
3597-6 ECU Power Output Supply Voltage #1 : Current Above Normal	1028-6 Power Supply Control 1 : Current Above Normal	A failed power supply to the power mode relay has been detected.

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Turn the keyswitch to the ON position. B. Connect Cat® Electronic Technician (ET) to the service tool connector. C. Turn the keyswitch to the ON position. D. Determine if a code is active or logged.	Codes	Result: A 3597-6 code is active. Proceed to Test Step 2.
2. Check for System Voltage at the Power Mode Relay Connector A. Turn the keyswitch to the OFF position. B. Disconnect the power mode relay from the wiring harness. C. Turn the keyswitch to the ON position. D. Measure the voltage between pin 5 on the power mode relay connector and a known good ground.	System Voltage	Result: System voltage was present at pin 5. The system is working properly. Verify the repair resolved the issue. Return to service. Result: System voltage was NOT present at pin 5. Proceed to test Step 3.
3. Check for an Open Circuit in the Power Mode Relay Wiring A. Turn the keyswitch to the OFF position. B. Disconnect the power mode relay from the wiring harness. C. Disconnect the J1 engine harness from the ECM. D. Measure the resistance between pin 5 on the power mode relay wiring harness connector and pin J1-21 on the ECM connector.	Open Circuit	Result: Less than 10 ohms of resistance between the pins. Proceed to Test Step 4. Result: More than 10 ohms of resistance between the pins. An open circuit has been detected. Repair: Repair or replace the wiring harness as necessary. Verify the repair resolved the issue. Return to service.
4. Check for a Short Circuit in the Power Mode Relay Wiring A. Turn the keyswitch to the OFF position. B. Disconnect the power mode relay from the wiring harness. C. Disconnect the J1 engine harness from the ECM. D. Measure the resistance between pin 5 on the power mode relay wiring harness connector and a known good ground.	Short Circuit	Result: More than 100 K ohms of resistance between pin 5 and a known good ground. Proceed to Test Step 5. Result: Less than 100 K ohms of resistance between pin 5 and a known good ground. A short circuit has been detected. Repair: Repair or replace the wiring harness as necessary. Verify the repair resolved the issue. Return to service.
5. Check for a Pin to Pin Short Circuit in the Power Mode Relay Wiring A. Turn the keyswitch to the OFF position. B. Disconnect the power mode relay from the wiring harness. C. Disconnect the J1 engine harness from the ECM. D. Measure the resistance between pin 21 on the J1 harness ECM connector and all other pins on the connector.	Short Circuit	Result: More than 100 K ohms of resistance between pin J1-21 and all other pins on the J1 ECM harness connector. Reconnect the power mode relay wiring harness and the J1 connector to the engine ECM. Proceed to Test Step 6. Result: Less than 100 K ohms of resistance between pin J1-21 and all other pins on the J1 ECM harness connector. A pin to pin short circuit has been detected. Repair: Repair or replace the wiring harness as necessary. Verify the repair resolved the issue. Return to service.
6. Check for Diagnostic Codes A. Start the engine. B. Connect Cat ET to the service tool connector. C. Determine if a code is active or logged.	Diagnostic Codes	Results: No codes are present. Return to service.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).