Automatic engine speed control function block diagram
The automatic engine speed control (AESC) function will allow the ECM to reduce the speed of the engine to low idle when no hydraulic system activity is detected. This aids in conserving fuel and reducing noise.
When the AESC switch on the soft switch panel is pressed, the ECM will monitor the "machine working function" in order to determine if hydraulic activity is needed. The ECM will initiate the AESC function when the machine working function indicates that there has been no hydraulic activity within 1 to 10 seconds. This time period is programmable in ET. The machine ECM sends the request for low idle directly to the engine ECM over the CAN data link. When any of the following functions are activated, the engine will return to the selected engine speed on the engine speed dial: swing, travel, implements (joysticks) and change of the speed dial position.
The operator can request that the engine go to low idle mode when the AESC function has not been enabled. When the low idle button on the right hand joystick is pressed, the ECM will check for hydraulic load conditions before sending a request for low idle to the engine ECM. The machine ECM will check the status of the swing pilot pressure switch and the main pump pilot pressure switch in order to determine if a request for hydraulic power is present. When both of these switches are open, the machine ECM will send the request for low idle to the engine ECM.
Note: The following paragraphs, which refer to the swash plate angle parameters, apply to machines in the following serial number ranges: BDR1-2000, BDM1-2000, BDX1-2000, BCZ1-2000, BDK1-2000, BDY1-2000 and BEB1-2000. For machines that are covered in this manual with a different serial number, if there is an active diagnostic code for the main pump pressure switch, the AESC function will be disabled.
A programmable parameter controls the deactivation of this function. The value of this parameter relates to the angle of the swash plate. This parameter is called the "Main Pump Swash Plate Angle Machine Operating Threshold" in ET. This value is normally 0.8 degrees greater than the angle of the swash plate, when the machine is not working. A change in the angle of the main pump swash plate that is greater than two degrees will deactivate the function. During this time, the idle of the engine will rise to the level that is set by the engine speed dial. If the angle is greater than 2 degrees, the time interval between actuating a control lever and the rise in the level of the engine idle will be delayed. For example, if the value is 4 degrees, check the value (standby or resting) of the main pump. Check the value by using the monitor or ET (status group 3). If this value is 3 degrees, the parameter is programmed at 1 degree above the angle (standby or resting) of the swash plate of the main pump.
If there is a diagnostic code for the sensor for the swash plate angle, then the automatic engine speed control does not function. The machine ECM checks the signal circuit (wire H783-GN) for proper operation. If the machine ECM detects an abnormal condition in the circuit, a diagnostic code will be activated.