164 RENR5042-02 Troubleshooting Section PTO switches The “PTO Mode” parameter The PTO switches enable the PTO speed control function and the PTO switches control the desired engine speed. The “PTO Mode” parameter determines the mode of operation. There are two modes of operation: “Ramp Up/Ramp Down” and “Set/Resume”. Use the Caterpillar Electronic Technician (ET) in order to change the value of the parameter. “Ramp Up/Ramp Down” Mode This mode uses three inputs. The inputs are provided by two switches. Refer to Illustration 80.
g01121879 Illustration 80 Schematic for the PTO inputs for the “Ramp Up/Ramp Down” mode of operation Placing the PTO Enable switch to the “Enable” position transfers the control of the desired engine speed from the throttle position sensor to the PTO speed control function. The PTO Ramp Up/Down switch controls the desired engine speed. If the “PTO Ramp Up” and “PTO Ramp Down” inputs are connected to the −Battery at the same time, the ECM will ignore the inputs. The desired engine speed will not change. “Set/Resume” Mode The PTO Ramp Up/Down switch is spring loaded to the normally open position.
When the switch is held in the “Ramp Up” position, the desired engine speed increases according to the value of the “Engine Accel Rate” parameter. When the switch is released, the desired engine speed maintains the set speed. After the desired engine speed has been set, momentarily placing the switch in the “Ramp position increases the desired engine speed by 20 rpm. This mode uses four inputs. The inputs are provided by three switches. Refer to Illustration 81. When the PTO Ramp Up/Down switch is held in the “Ramp Down” position, the desired engine speed decreases according to the value of the “Engine Accel Rate” parameter.
When the switch is released, the desired engine speed maintains the set speed. After the desired engine speed has been set, momentarily placing the switch in the “Ramp Down” position decreases the desired engine speed by 20 rpm.