This subpart applies to manufacturers of passenger cars, and of trucks and multipurpose passenger vehicles with a gross vehicle weight rating (GVWR) of 3,855 kilograms (8,500 pounds) or less, and of buses with a GVWR of 4536 kg (10,000 lb) or less, for which Standard No. 225 (49 CFR 571.225) applies. However, this subpart does not apply to vehicles excluded by S5 of Standard No. 225 from the requirements of that standard.