(Page 4 regarding P1)
In this mode M3-ATX sends ON pulse to motherboard when ignition is ON
for more than 2 seconds. After ignition is turned off first time since the PSU running the PSU waits 1 minute in case of the user changes his mind and turns back ON the ignition. If the ignition remains turned off in this extra 1 minute timeout the PSU sends OFF pulse to motherboard after 5 seconds later. As a result in P1 mode the PSU begins to turning off the motherboard after a total time of ~1 minute and 5 seconds.