AFTERCOOLER 6I1188 - Caterpillar

Auxiliary Hydraulic Control Operation
Each control lever installed on the machine contains an internal position sensor. When powered up, that sensor sends a constant Pulse Width Modulated (PWM) signal to either the Implement ECM or the "Implement ECM 2". The ECM that the particular signal circuit is connected to depends on the control levers that are installed. Each installed lever position sensor circuit is monitored by the ECM for diagnostics. If the ECM detects a problem in the signal circuit, the ECM will activate a diagnostic code for the circuit.The duty cycle of the control lever PWM sensor signal changes depending on the direction and the amount of lever movement. Duty cycle is the percentage of time a signal is high, compared to the percentage of time the signal is low, for one full cycle. The duty cycle signal from a typical position sensor the ECM will recognize as valid is from 10 ( 5) percent to 90 ( 5) percent. That range of Duty Cycle percentage is measured at the extreme ends of lever travel. A control lever that is in the center or the neutral position would result in a duty cycle signal of approximately 50 5 percent.The ECM uses the PWM duty cycle signals received from a control lever to control two proportional solenoids, for an assigned auxiliary hydraulic valve. The ECM will use a PWM output signal in order to control the amount of electrical current that is sent to the solenoids. When the PWM duty cycle signal from the lever position sensor changes, the ECM adjusts the amount of current that is sent to the solenoids. The current sent to the solenoids determines the amount of pilot oil pressure directed to the hydraulic valve to move the valve spool. An increase in the amount of electrical current that is applied to the solenoids will increase the movement of the valve spool. The movement of the valve spool will result in more hydraulic oil flow to the hydraulic cylinder for the implement. When the lever is in the neutral position, the duty cycle is approximately 50 percent. At this level, the ECM outputs a small current which is not enough to cause the valve spool to move. This small current output to the solenoid enables quicker response time when a move is requested.Advanced Control Joystick (ACJ) Position Sensors
When the ACJ thumbwheels are configured as Lever 8 and Lever 9 for control of Auxiliary Hydraulic Circuits, the duty cycles will be:Lever No. 8 - Assigned to the "thumbwheel" on the left-hand ACJ. The sensor signal duty cycle will be approximately 5% to 45% when the "thumbwheel" switch is at the full lower position. The duty cycle will be approximately 55% to 95% when the "thumbwheel" switch is at the full upper position. When the "thumbwheel" switch is in the center position, the duty cycle will be approximately 50% ( 5). The Implement ECM will interpret a duty cycle below 5% as "shorted low" and a