Seems it outta work (with rattlebar's schematic). *P* to me means *Port*. That is, that particular prong is normally wired directly to the blinker's idiot light (port) on the dashboard, meant for cars. It taps the flasher pulses itself, so Left or Right signal is moot. You'll have to test for continuity between the L and the P prongs. If there is continuity there'll be cross feed at their internal confluence. If no continuity, than there's a internal diode wired integral to the P or L prong.
Oh btw if you were to replace the Oem flasher with a L/X/P flasher, it actually eliminates unintended 4-way flashing, in place of the diode solution,
though you still have to join the left/right wires together on the idiot light, and configure a ground wire. I just haven't found a Port flasher that blinks at the proper rate at least to my eyes. With leds on the front signals only, the flashing was okay. With leds on the front and the rears, the activated side's flashing was retarded, but for a 4-way flashing mode it's probably not an issue.
Below, equivalent schematic (my apologies for the subthread).
