06-up use a PPC solenoid, not PWM. PPC="Pressure Proportional to Current". PWM uses a low frequency square wave, in the 100Hz realm IIRC, to drive a coil that limits current due to it's DC resistance. PPC uses much higher frequency, around 1KHz, and drives a low resistance coil. Current is limited by the solenoids impedance. Impedance is an AC quantity, being a sum of the coils AC reactance (reactance is the resistance of flow to alternating current, and is frequency dependent) and DC resistance (resistance works for both DC and AC). With any electrical inductor (which is what a solenoid is), there is a maximum amount of "on" time that can be tolerated, which is dependent on it's construction. Too much on time will saturate the inductor, at which point it's AC reactance drops sharply and current is mainly limited by the DC resistance. Since the DC resistance in a PPC solenoid is comparatively low, compared to a solenoid designed for PWM duty, the resulting current will be high, which will overheat and destroy the solenoid. That is why the duty cycle is limited to only 65%. With a PPC solenoid, 65% duty cycle will give 100% open (or close, as the case may be). Any more gives no extra flow, and just risks saturating and overheating the solenoid. Between 0 and 65%, the current through the solenoid increases in a fairly linear manner with increasing duty cycle, which is supposed to open (or close) the valve an approximately proportional amount.
This ^^^. You'd think if the TCM was truly commanding the TC to lock and did not see the appropriate RPM drop, it would throw a code
