TOKYO, Feb 4 - Japan's Nikkei average <.N225> fell to a six-week low on Wednesday as a weakening dollar raised concerns about a strong yen crimping corporate earnings and spurred selling of Canon Inc <7751.T> and other exporters. Bank issues continued to lose ground on growing worries about bad loans after financial sources said last week that Japan's Financial Services Agency would step up its investigation of the loans book at UFJ Bank, a unit of UFJ Holdings Inc <8307.T>. The Nikkei average <.N225> closed down 1.83 percent at 10,447.25, the lowest since December 26. It was the biggest one-day percentage fall since December 16. The broader TOPIX index <.TOPX> also fell 1.98 percent to 1,022.61.||