"Squeaking pedals" can be so many different things that it's hard to write them all down. Basically, you have to disassemble every metal-to-metal joint, clean it, lube or Loctite it, and then see if it fixes the noise. I once spent a month trying to track down a squeak, taking apart my bottom bracket, cranks, pedals, headset, seat, whatever. Eventually I cleaned and re-greased the pedal threads before reinstalling them. That cured the squeak.