Got a request from a guy to help him do a propane swap on 1 MB LS1 PCM. I believe he is mainly looking to increase the timing maps when the propane is on. I was thinking of using the flexfuel maps in the OS to accomplish this goal. The question I have is about the flex fuel sensor input. I'm pretty sure it is a PWM signal that tells the PCM the ethanol percentage. I don't have a sensor and am just looking to make a switch between gasoline and propane. Can I just feed the PCM a switched (on / off) signal instead of a PWM?