(a) As a condition of certification, the retrofit/rebuild equipment certifier shall warrant that if the certified equipment is properly installed and maintained as stated in the written instructions for proper maintenance and use, the equipment will not cause an urban bus engine to exceed the emission requirements of this subpart and the emission standards set forth in 40 CFR part 86. This retrofit/rebuild equipment warranty shall extend for a period of 150,000 miles from when the equipment is installed.

(b) As a condition of certification, the retrofit/rebuild equipment certifier shall provide an emissions defect warranty that if the certified equipment is properly installed and maintained as stated in the written instructions for proper maintenance and use, the equipment certifier will replace all defective parts, free of charge. This emissions defect warranty shall extend for a period of 100,000 miles from when the equipment is installed.