The Abwehr sent a Serbian count who used his cover as an international business man to run various agents and obtain information to the US to form a spy network there. He was told by the Germans to gather information on the defenses at Pearl Harbor and given a deadline for obtaining the information, as that was the week the attack was planned for.

Unknown to the Abwehr, the count had gone to the British as soon as the Germans tried to recruit him, and was relaying MI6 approved material. Worse yet for the Germans, he had turned his Abwehr handler, a high ranking and well connected member of the primary German intelligence service. The count, whose code name was Tricycle (the code name referred to his frequent enjoyment of menage a trois), informed MI6 of the plot. They in turn arranged to have him meet Hoover. He met with Hoover on August 12, 1941, months before the attack. After the meeting, he was kicked out of the country on the pretense that he had violated the Mann act by transporting a well known actress from Florida to New York (it was illegal to bring a women across state lines and have sex with them).

Tricycle's exploits have been well documented - both in his own memoirs and in several books about the role of MI6 in World War II. Ian Fleming credited Tricycle with being an inspiration for James Bond character.

I know a lot less about the Japanese source.