Currently, smog inspections are required for most vehicles every two years for registration renewal.
Diesel Vehicles:
All diesel vehicles 1998 model or newer or an GVWR of less than 14,000 lbs must undergo smog inspections.
Exemptions:
1. Gasoline powered 1975-year model or older
2. Electric
3. Natural gas powered with a GVWR rating of more than 14,000 lbs.
4. Owners of vehicles less than 4 model years old can pay an Annual Smog Abatement Fee for the first 8 registration years instead of being required to provide a biennial smog certification.
For more information visit: https://www.dmv.ca.gov/portal/
For information on Kit and Specially Constructed Vehicles visit: https://www.dmv.ca.gov/portal/vehicle-registration/new-registration/register-a-specially-constructed-or-modified-vehicle/
California Vehicle Code
§ 27150. Adequate muffler required
(a) Every motor vehicle subject to registration shall at all times be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and no muffler or exhaust system shall be equipped with a cutout, bypass, or similar device.
§ 27151. Modification of exhaust systems
(a) No person shall modify the exhaust system of a motor vehicle in a manner which will amplify or increase the noise emitted by the motor of the vehicle so that the vehicle is not in compliance with the provisions of Section 27150 or exceeds the noise limits established for the type of vehicle in Article 2.5 (commencing with Section 27200). No person shall operate a motor vehicle with an exhaust system so modified.
(b) For the purposes of exhaust systems installed on motor vehicles with a manufacturer’s gross vehicle weight rating of less than 6,000 pounds, other than motorcycles, a sound level of 95 dbA or less, when tested in accordance with Society of Automotive Engineers Standard J1169 May 1998, complies with this section. Motor vehicle exhaust systems or parts thereof include, but are not limited to, nonoriginal exhaust equipment.
Historic Vehicle
Available for vehicles manufactured after 1922 which are at least 25 years old and of historic interest.
Horseless Carriage
Available for vehicles with an engine of 16 or more cylinders that were manufactured prior to 1965 and for vehicles manufactured in 1922 or earlier, regardless of cylinders.
Legacy
Replicas of California license plates similar to those issued in the 1960s. Legacy license plates can be ordered for any year model automobile, commercial vehicle, motorcycle, or trailer.
YOM
Vehicles manufactured in 1980 or earlier may display YOM plates with DMV approval.