The 2003 Infiniti M45 was designed in 2000 at the Nissan Technical Center (NTC) in Atsugi, Japan; was manufactured in Tochigi, Japan; and is based on the Y34-series Nissan Gloria. The M45 allowed Infiniti to expand the use of the 4.5L V8 that had been exclusive to the Q45, thus creating a better economy of scale to cope with that engine's development costs.
The Infiniti M uses a much more rigid version of the G35/350Z/FX Nissan FM platform and was available with the common VQ-series 280 hp (208 kW) 3.5 L V6 in the M35, or the Q45's 335 hp (249 kW) 4.5 L V8 in the M45. This generation of the Infiniti M was sold in Japan as the Nissan Fuga.
The first-generation Infiniti M45 was sold for 2003 and '04 -- there was no 2005 model. The most recent generation of the Infiniti M45 was produced from 2006 to 2010. The M45 was replaced by the redesigned M56 for the 2011 model year.