Test running began on the Ōu Main Line between and on 14 November 1990. From 23 January 1991, test running began in conjunction with a newly converted 200 series 8-car K set on the Tōhoku Shinkansen between and . On 26 March 1991, the 400 series set S4 established a new Japanese speed record of 336 km/h on the Jōetsu Shinkansen in the Yuzawa Tunnel between and . On 19 September 1991, the train set a new speed record of 345 km/h on the same stretch of track.