Toyota Mark X late 1960s. Instead of being based on a modified Supra chassis "A" series platform, the Mark X continues to use the Toyota "X" platform, and does not share its platform with the Toyota "S" series platform used under the Toyota Crown and the Lexus GS. The continuation of describing this vehicle as the "X" series is a reference to the first dedicated Mark II platform introduced in 1972. Major changes to the Mark series are the engine and footwork. Toyota discontinued the straight-six engines used in the Toyota Verossa, which included the JZ series and the G series engines, and
2009–11 Toyota vehicle recalls mat entrapment and pedals that were slow to return to idle as two causes of Toyota complaints. NHTSA also stated it could only verify one Toyota unintended acceleration accident caused by a vehicle defect. On July 14, 2010, the "Wall Street Journal" reported that NHTSA investigations of 75 accidents alleged to sudden acceleration in Toyota vehicles had found driver error as the primary cause in all but one case attributed to floor mats. Black box recorder data found that during these crashes, the throttle was open and brakes not pressed. On July 30, the "Wall Street Journal" quoted the former