HORN 6C5859 - Caterpillar

Probable Causes
Diagnostic codes and event codes
Cold mode operation and cold cylinder cutout
Flash file
Throttle switch
Injection actuation pressure
Electrical connectors
Unit injectors
Boost pressure sensor
Air inlet and exhaust system
Fuel supplyRecommended Actions
Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine idle, full load, or a specific operating temperature. Troubleshooting the symptoms under other conditions may give misleading results.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/or logged codes. Troubleshoot any codes that are present before continuing with this procedure.Note: Although a sensor's signal may be in the operational range of the sensor, certain failure modes of a sensor may produce an output signal that does not represent an accurate measurement. Use Cat ET to check that the pressures and the temperatures are fluctuating normally. Also check that the values are reasonable for the conditions that are present.Cold Mode Operation and Cold Cylinder Cutout
Use Cat ET to verify that the engine has exited cold mode. Cold mode operation may cause a slow throttle response. Some engines use a feature such as the cold cylinder cutout in order to warm the engine during cold mode. Again, ensure that the engine has exited cold mode operation.Personality Module (Flash File)
Verify that the latest flash file has been installed into the ECM.Throttle Switch
Monitor the status of the throttle switch on Cat ET. Verify that the throttle switch is operating correctly. Refer to Troubleshooting, "Throttle Switch Circuit - Test" for the proper troubleshooting procedure.Injection Actuation Pressure
Check the engine oil level. Engine oil supplies the injection actuation pressure circuit. The engine oil must be kept at the proper level for fuel injection.
If service has recently been performed on the engine, air may be present in the injection actuation pressure circuit. Allow the engine to fully warm up and operate the engine under load in order to purge the air from the injection actuation pressure circuit.
Check the injection actuation pressure. Refer to Troubleshooting, "Injection Actuation Pressure - Test" for the correct procedure.
Check the operation of the injection actuation pressure control valve. Refer to Troubleshooting, "Injection Actuation Pressure Control Valve Circuit - Test" for the proper troubleshooting procedure.Electrical Connectors
Disconnect the J1/P1 and J2/P2 ECM connectors. Inspect each connector for moisture and corrosion. Also, inspect the harness and connectors for the unit injectors from the ECM to the valve cover. Refer to Troubleshooting, "Electrical Connectors - Inspect".Unit Injectors
Use Cat ET to perform the injector solenoid test in order to determine if all of the injector solenoids are being energized by the ECM.
Perform the cylinder cutout test on Cat ET in order to check the performance of each cylinder. Refer to Troubleshooting, "Injector Solenoids Circuit - Test" for the correct procedure.Boost Pressure Sensor
Monitor the status of "Fuel Position", "Rated Fuel Limit", and "FRC Fuel Limit" on Cat ET while the engine is operating under full load. These parameters should agree with the information below.
Table 1
"Fuel