The EPA doesn't have to OK any tech. As long as a vehicle meets EPA and CAFE standards when sold it's good to go.
I have to dispute that comment. EPA does follow-up testing on in-use vehicles to make sure the emission controls are still working properly. When I ran a municipal fleet, they contacted us a couple of times to get vehicles to test. This quote is from a story about Cummins recalling 500k medium/heavy truck engines in 2018"
At the fleet level they may do "follow up" but that doesn't mean they had to OK the "tech" before it was sold. The goal of OBDII was to insure emissions levels stay near the limits the vehicle had to meet when tested new.
I agree that there's no "approval" by the EPA. The second sentence is incorrect. From the EPA website at:
Link"Vehicle, engine, and equipment manufacturers are required to design and build their vehicles, engines, and equipment to meet emission standards for the useful life of the vehicle, engine or equipment specified by law."
They define useful life as 7-8 years and 100-150k miles.
