As before, the engine was based on the 4G63 model. From the opening round, Monte Carlo Rally, in January, a new wastegate and anti-lag valve were used, while the engine management was improved. The combination of these improvements significantly raised the level of performance and provided for a refined tuning. In addition, the newly adopted semi-automatic gearbox and clutch enabled clutchless gear shifting via a paddle attached to the steering wheel. As announced the previous year, drivers Harri Rovanperä (Finland), Gilles Panizzi and Gianluigi Galli (Italy) were lined up for the rally season.
Panizzi finished third in the season’s opening rally in Monte Carlo. The MITSUBISHI MOTORS team achieved their first podium position, three years and a half after the last one they claimed at the Safari Rally in July 2001. Top driver Rovanperä consistently reached the finish, scoring points in nine out of 16 races, and demonstrated a high level of constancy. In October, MITSUBISHI MOTORS participated in the WRC held on home soil for the first time, competing with a three-car lineup in the 13th round, Rally Japan. It was MITSUBISHI MOTORS' first monumental battle in their home country of Japan and they entered the rally in full force by sending in all of their contracted drivers. In that rally, Rovanperä finished fifth, a result that greatly excited the Japanese fans. In the 16th and final round, Rally Australia, Rovanperä finished second overall, which was the highest position for the team that season, and Galli finished 5th overall, equaling his personal best to date. These results proved that the LANCER WRC05 was steadily making progress.

In December, MITSUBISHI MOTORS announced that they needed to focus more on the selection and concentration of management resources, and that they would suspend their participation in the WRC from 2006 to concentrate on participating in the Dakar Rally, in which they were on a five-race winning streak. Their philosophy, which is "continuing to fight at the forefront of rally competitions will always be useful for the development of production vehicles, which are MITSUBISHI MOTORS' products" has brought changes in four-wheel control technology and electrification technology, and its effect is still being passed down to their production vehicles such as SUVs.