40 CFR §85.2201

1. (a)This subpart describes the test provisions to be employed in conjunction with the Emissions Performance Warranty in subpart V of this part. These provisions generally rely on a vehicle's onboard diagnostic system (OBD) to indicate whether a vehicle passes or fails the test.
2. (b)The provisions of this subpart may be used to establish warranty eligibility for light-duty vehicles, light-duty trucks, and medium-duty passenger vehicles when tested during the useful life as prescribed in subpart V of this part.