California Law on Car Modifications Part 1

California car enthusiasts love to modify their cars, from exhaust systems to window tinting to neon underglow lighting.  Before you make any modifications to your car be sure to check whether California prohibits your desired modification.  The following will briefly review several of the more popular vehicle modifications:

Illegal: Loud Exhaust Systems

If you want people to hear your car before they see it, make sure it’s not illegal to have a loud exhaust.   Many car enthusiasts want to modify their car’s exhaust system, but there are laws governing the noise limit your vehicle can produce. California changed its exhaust law in 2019 so that having a loud muffler is no longer just a fix-it ticket but rather a ticketed fine. In short, vehicles must have a muffler that prevents “excessive noise from the exhaust system.”

If you’re driving a passenger vehicle — other than a motorcycle — or a truck weighing less than 6,000 pounds, the exhaust can’t be louder than 95 decibels, according to the California Bureau of Automotive Repair.

California Vehicle Exhaust Noise Laws

The sections below outlines relevant California laws that apply to car exhaust noise:

California Vehicle Code § 27150 – 27153 (2019)

Vehicle Code 21750. Adequate muffler required

  1. (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.

And

Vehicle Code 27151. Modification of exhaust systems

  • 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.
  • 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, non original exhaust equipment.

To briefly summarize these two (2) California code sections:  All cars and other motor vehicles in California must be equipped with an adequate muffler; and any exhaust system modifications must not be designed to increase the exhaust noise level above 95 dbA.

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