Duty Cycle, Frequency and Current Flow: Notes

A duty cycle may be defined as the percentage of time current is flowing through a solenoid coil during each cycle. The number of cycles that occur within a specified amount of time, usually measured in seconds, is called 'frequency.' Typically, the operation of an electronically controlled pulse width modulated solenoid is explained in terms of duty cycles and frequency.

The TCM controls the PC solenoid valve on a positive duty cycle at a fixed frequency of 292.5 Hz cycles per second. A higher duty cycle provides a greater current flow through the solenoid. The high positive side of the PC solenoid valve electrical circuit at the TCM controls the PC solenoid valve operation. The TCM provides a ground path for the circuit, monitors average current and continuously varies the PC solenoid valve duty cycle to maintain the correct average current flowing through the PC solenoid valve.

The duty cycle and current flow to the PC solenoid valve are mainly affected by throttle position and engine torque. As the throttle angle engine torque increases, the duty cycle is decreased by the TCM which decreases current flow to the PC solenoid valve. Current flow to the PC solenoid valve creates a magnetic field that moves the solenoid armature against spring force.