861590A05 Mercruiser HOSE ASSEMBLY, Circulating Pump to Thermostat Housing

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Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high rpm, full load and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.Programmable Parameters
Verify that the complaint is not due to a normal operation such as a programmed parameter. Connect the electronic service tool and verify that the parameters are programmed correctly.Diagnostic Codes and Event Codes
Certain diagnostic codes and/or event codes may cause poor performance. Connect the Caterpillar Electronic Technician (ET) and check for active codes and for logged codes. Troubleshoot any codes that are present before continuing with this procedure.Injector Trim Codes
If any of the injectors or the Electronic Control Module (ECM) have been replaced, ensure that the injector trim codes have been programmed to the correct values. Refer to Troubleshooting, "Injector Code - Calibrate" for additional information.Engine Rating
Verify that the correct engine rating is being used for the application.Programmable Parameters
Check the following parameters on Cat ET:
Throttle Position SensorDetermine the type of throttle that is used in the application. Program the parameters to match the type of throttle that is used. Refer to Troubleshooting, "Throttle Position Sensor Circuit - Test" for more information.Note: The engine will have poor performance if the parameters are not programmed correctly.Cold Mode
Monitor the status screen on Cat ET in order to verify that the engine has exited cold mode. Observe the reading for coolant temperature on Cat ET. Refer to Troubleshooting, "System Overview" for additional information.High Exhaust Temperature
The engine may be derated due to high exhaust temperature. Connect Cat ET to the service tool connector. Check for an active engine derate on the status screens.Note: High exhaust temperature is a calculated value. The engine does not have an exhaust temperature sensor.Electrical Connections to the ECM
Check the following connectors for proper installation:
J1/P1 and J2/P2 ECM connectors
J61/P61 Customer connectors
J300/P300 Connectors for the injector solenoid harness
J401/P401 and J402/P402 Engine Speed/Timing Sensor connectors
Check the associated wiring for the following conditions: damage, abrasion, corrosion and incorrect attachment.Refer to Troubleshooting, "Electrical Connectors - Inspect".Note: Aftermarket engine protection devices usually interrupt power to the ECM. Check for correct installation and for operation of aftermarket engine protection devices. It may be necessary to bypass the aftermarket devices in order to continue testing.PTO Enable Switch
Verify that the "PTO Enable Switch" is "Not Engaged". If the value of the parameter does not match the position of the switch, there is a problem with the circuit for the PTO enable switch. Refer to Troubleshooting, "Switch Circuits - Test".If the value of the "PTO Enable Switch" parameter matches the position of the switch, continue to next step.Intermediate Speed Switch
Verify that the value of the "Intermediate Speed Switch" matches the position of the switch. If the value of the parameter does not match the position of the switch, there is a problem with the circuit for the switch for the intermediate speed. Refer to Troubleshooting, "Switch Circuits - Test".If the value of the "Intermediate Speed Switch" parameter matches the position of the switch, continue to next step.Throttle Signal
View the status for the throttle position on the status screen. Operate the throttle from the low idle position to the high idle position. The status should be 0 percent at low idle and the status should be 100 percent at high idle. If the status cannot operate in the full range, refer to Troubleshooting, "Throttle Position Sensor - Calibrate".Diagnostic codes that are related to the J1939 data link will prevent correct operation of the throttle if the throttle position is transmitted over the data link. If there is a problem with the data link, the engine will remain at low idle until the data link is repaired.Circuit for the Electronic Unit Injector
Inspect the J2/P2 ECM connector and the J300/P300 unit injector connector for proper connections. Refer to Troubleshooting, " Electrical Connectors - Inspect". Cut out each cylinder in order to isolate the misfiring cylinder or cylinders. If the results are inconclusive, shut off half of the cylinders and repeat the cylinder cutout test on the active cylinders that are remaining in order to locate those cylinders that are missing. Refer to Troubleshooting, "Injector Solenoid Circuit - Test".Fuel Supply
Check for a problem with the fuel supply. Verify that the fuel pressure is correct. Verify that the fuel pressure sensor P209/J209 is installed. For further information, refer to Systems Operation/Testing and Adjusting, "Fuel System".Boost Pressure Sensor, Rated Fuel Position and/or FRC Fuel Position
With the engine at full load, monitor "Fuel Position" and "Rated Fuel Limit" on the status screen. If "Fuel Position" does not equal "Rated Fuel Limit", then check the boost pressure.
Verify that there are no active diagnostic codes that are associated with the boost pressure sensor or with the atmospheric pressure sensor.
Monitor the boost pressure and the atmospheric pressure for normal operation on the status screen.Note: Atmospheric pressure is not a default parameter on the status screen.Air Inlet and Exhaust System
Check the air inlet and exhaust systems for restrictions and for leaks. Refer to Systems Operation/Testing and Adjusting, "Air Inlet and Exhaust System". Replace the plugged air filters or clean the plugged air filters according to the guidelines in the engine's Operation and Maintenance Manual. Repair any leaks that are found in the system.