3406E, C12, C15 and C18 Marine Engines Caterpillar

Probable Causes

• Active engine derate

• Throttle signal

• Electrical connectors

• Fuel supply

Recommended Actions

Active Engine Derate

If an active derate occurs, the warning lamp will flash. "Engine Derate" will appear in the first box for engine status on the status screen of Caterpillar Electronic Technician (Cat ET). Verify that the set points for "Derate" that are in the Programmable Monitoring System have been programmed to the values that are correct. An SPN-FMI code will appear for an active derate on a display device for the J1939 data link.

Throttle Signal

Verify that the "Maximum Trolling Engine Speed" and "Low Idle Speed" are programmed to the values that are correct. Monitor the parameters for the throttle on the Cat ET. Use Table 1 to monitor the parameters.

The "Desired Engine Speed" and the "Throttle Position" should increase linearly. Both parameters should increase steadily to the Programmed "high idle". The Desired Engine Speed and the Throttle Position should decrease linearly. Both parameters should decrease steadily to the Programmed "low idle". Refer to Troubleshooting, "Throttle Position Sensor Circuit - Test" for additional information.

Electrical Connectors

1. Use Cat ET to check for the following diagnostic code.
   • CID 168-FMI 02, SPN 168-FMI 02, Flash 51 System Voltage intermittent/erratic

   If this diagnostic code is active or logged, refer to Troubleshooting, "Electrical Power Supply Circuit - Test".

2. Inspect the battery wires from the ECM back to the battery compartment. Refer to the Electrical System Schematic. Inspect the wires and the power relay. Check the power and ground connections to the ECM. Refer to Troubleshooting, "Electrical Power Supply Circuit - Test" for more information.

Fuel Supply

1. Check the fuel lines for the following problems: restrictions, collapsed lines and pinched lines. If problems are found with the fuel lines, repair the lines and/or replace the lines.

2. Check the fuel tank for foreign objects which may block the fuel supply.

3. Check for air in the low pressure fuel supply system if any of the following procedures have been performed:
   • Replacement of the fuel filters

   • Service on the low pressure fuel supply circuit

   • Replacement of unit injectors

   Note: A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel. Refer to Testing and Adjusting for more information.

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NOTICE
Do not crank the engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again.

4. Purge air from the low pressure fuel supply circuit. Refer to Operation and Maintenance Manual, "Fuel System - Prime" for the correct procedure.

5. Check fuel quality. In temperatures below 0 °C (32 °F), check for solidified fuel (wax). Refer to Special Instruction, SEBD0717, "Diesel Fuels And Your Engine".

6. Check the fuel pressure after the fuel filter while the engine is being cranked. Refer to Testing and Adjusting for the correct pressure values. If the fuel pressure is low, replace the fuel filters. If the fuel pressure is still low, check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve. Refer to Testing and Adjusting for more information.