Sustain pedal does not work

SOURCE: Sustain pedal not working on my Yamaha P-90

What I figured out is that when i turn on the keyboard, if i hold down the pedal by accident, it will work in reverse. I dont know if this is what you mean. If it is, just dont touch the pedal when you turn it on. If it isn't, try to return the pedal. I dropped one, it had this problem, and they gave me a new one. Your cord for it might have been bent (?). Also, turn the keyboard on with the pedal already plugged in. It's not made to be plugged in while it's on. Hope this helps. - Matthew

SOURCE: hello- my P95 sustain pedal

This is confusing... you say "the sustain works when you disconnect the cord"? How can that happen? and doesn't work when it is plugged in.

MOST sustain pedal problems are due to people using a different pedal than the keyboard is designed to use. It is very common that someone tries to use a Roland sustain pedal on a Yamaha and oof course it doesn't work because the Roland pedal is normally closed and Yamaha usually requires a normally open contact.

A FEW keyboards now check the state of the pedal input when power is first turned on and configure the pedal polarity accordingly. For these keyboards, make sure the pedal is plugged in before power is turned on.

SOURCE: Fc4 sustain pedal is in

Sorry, but the Yamaha pedal has the opposite sense (it is a normally open contact) than what is REQUIRED by Roland equipment. Roland requires a Normally Closed contact. Unfortunately, one is confused because the Roland jack for the sustain shorts itself to no sustain when you unplug a pedal. SOMETIMES one can open a pedal and with soldering iron change a wire to reverse the pedal sense IF the particular pedal has both contacts available.