The 27 year old Senegal international was charged with failing to supply information on who was driving on both occasions.
Police would not release details of the vehicle involved, locations or speed, but did confirm that there had been two "speeding offences".
The court was told the player had failed to attend two previous hearings and ignored police letters sent in November 2011 asking him to confirm who was driving his car on the two occasions in question.
The former West Ham player was also fined £1,000, told to pay £85 costs and a £15 victim surcharge.
Newcastle United declined to comment on the case.