27150. (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. (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.
You can be cited for one or both of these sections.