LOCKNUT 3J6899 - Caterpillar

The Electronic Control Module (ECM) provides control of the air/fuel mixture for maximum performance and for efficiency at low emission levels. The system includes several factors: maps in the ECM, output drivers in the ECM, sensors and customers input via the Caterpillar Electronic Technician (ET).
Table 1
Tools Needed     Qty    
391-8170 EMISSIONS ANALYZER TOOL GP - (Bluetooth Module) (1)     1    
393-0673 EMISSIONS ANALYZER TOOL GP (1)     1    
( 1 ) Either emissions analyzer may be used. Illustration 1 is a diagram of the systems main components.
Illustration 1 g01456978
Diagram of the system for the air/fuel ratio controlTo accurately control the air/fuel ratio, the ECM depends on the following parameters that are programmed via the "Configuration" screen of Cat ET. For details on these parameters, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".
"Fuel Quality"
"Gas Specific Gravity"
"Fuel Specific Heat Ratio"
"Emissions Feedback Mode Configuration"
"Desired Engine Exhaust NOx Level Setting"
"Air/Fuel Proportional Gain"
"Air/Fuel Integral Gain"Note: Some fuel metering valves utilize the "Gas Specific Gravity" and the "Fuel Specific Heat Ratio" parameters. The fuel metering valve uses this information to help regulate the fuel flow.The air/fuel ratio control has two basic modes of operation:
Open loop
NOX feedbackThe mode of operation is determined by the "Emissions Feedback Mode Configuration" parameter. Cat ET is used to change the mode of operation.Select "Disable" in order to activate the open loop mode.Select "Enable" in order to activate the feedback mode.The modes of operation are explained below.Open Loop
Illustration 2 g01457790
Diagram of the open loop mode (no feedback)Open loop - During operation in this mode, the ECM does not use any feedback for determining the fuel command. The open loop mode is intended to be a temporary mode of operation. The open loop mode allows the engine to operate if the feedback system becomes inoperative. In this mode, the ECM cannot maintain consistent exhaust emissions. Input from an operator that is working with an exhaust analyzer is necessary for maintaining the exhaust emissions.For this mode of operation, the ECM performs several operations in order to determine the fuel command.Volumetric efficiency - The volumetric efficiency of an engine with a four stroke cycle is the relationship be