3126B Marine Engines Caterpillar

Note: If the vessel is equipped with a Multi-Station Control System (MSCS), refer to Service Manual, RENR7651, "Marine Multi-Station Control System" for the proper troubleshooting procedure.

Note: Use this procedure only if the engine shut down completely and it was necessary to restart the engine.

Probable Causes

• Diagnostic codes

• Electrical connections

• Remote shutdown switch

• Fuel supply

Note: If the problem only occurs under certain conditions such as high engine speed, full load or engine operating temperature, then perform the test under those operating conditions.

Recommended Actions

Diagnostic Codes

Certain diagnostic codes may cause the engine to shutdown. Connect the electronic service tool and check for active codes and/or logged codes. Troubleshoot any codes that are present before continuing with this procedure.

Electrical Connections

1. Check the following connectors and the associated wiring for damage, for abrasion, for corrosion and for incorrect attachment:
   • ECM connectors

   • Customer connectors

   • Engine speed/timing sensors

   • unit injector connectors

   Refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information.

2. Check the battery connections at the customer connector and the P1 ECM connector. Perform a pull test on all of the wires that are related to the battery connections. Refer to the engine's Electrical Schematic for the appropriate terminals. The wires should remain in the connectors during the pull test. Refer to Troubleshooting, "Electrical Connectors - Inspect".

3. The problem may occur when the engine is warmed up. Then as the engine cools, the problem may disappear. The circuit breakers may be exceeding the trip point because of the overheating. Check the circuit breakers on the engine. Reset the circuit breakers, if necessary.

4. Aftermarket engine protection devices can interrupt power to the ECM. Check for correct installation and operation of aftermarket engine protection devices. It may be necessary to bypass aftermarket devices in order to continue testing.

Fuel Supply

Check for a problem with the fuel supply and verify the fuel pressure. Verify that the fuel pressure sensor is installed. Refer to Systems Operation/Testing and Adjusting, "Fuel System" for additional information.

Remote Shutdown Switch

Access the status screen on the electronic service tool that displays the remote shutdown switch status. The remote shutdown switch status on the electronic service tool is called "User Shutdown".

Table 1

"User Shutdown" Status	Switch Status	Measured Voltage at P61-36
ON	Negative battery	<0.9 VDC
OFF	Open Circuit	>10 VDC

If the voltage is not in the proper range, refer to Troubleshooting, "Switch Circuits - Test".