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Illinois Exhaust & Muffler Laws (2026)

Info: Your vehicle needs an adequate muffler and exhaust so it doesn't make excessive or unusual noise, and cutouts and bypasses (which route exhaust around the muffler) are prohibited, as are changes that increase noise.

InfoVerified Jun 19, 2026

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Your vehicle needs an adequate muffler and exhaust so it doesn't make excessive or unusual noise, and cutouts and bypasses (which route exhaust around the muffler) are prohibited, as are changes that increase noise. Illinois sets no fixed decibel limit (625 ILCS 5/12-602).

Official source: ilga.gov →

General legal information, not legal advice — verify important decisions with a licensed attorney.

Exhaust & Muffler in states bordering Illinois

The same rule in each neighboring state LawLert has verified, from that state’s own official source.

IndianaInfo
Your vehicle needs a muffler in good working order, and cutouts and bypasses (which route exhaust around the muffler) are banned — the system can't leak or have altered parts. Indiana sets no fixed decibel limit (Ind. Code §§ 9-19-8-2, 9-19-8-3).
Verified Jul 30, 2026 · Source: iga.in.gov · Full Indiana rule →
IowaInfo
Your vehicle needs a muffler in good working order so it doesn't make excessive or unusual noise, and muffler cutouts and bypasses (which route exhaust around the muffler) are prohibited. Iowa sets no fixed decibel limit (Iowa Code § 321.436).
Verified Jun 19, 2026 · Source: legis.iowa.gov · Full Iowa rule →
KentuckyInfo
Your vehicle needs a suitable, efficient muffler; running with the cutout removed is prohibited, and so is any change that makes the exhaust louder than the factory setup. Kentucky sets no fixed decibel limit (KRS § 189.140).
Verified Jun 19, 2026 · Source: apps.legislature.ky.gov · Full Kentucky rule →
MissouriInfo
Your vehicle needs a properly attached muffler to quiet the exhaust, and muffler cutouts and excessive noise are barred — a violation is an infraction. Missouri sets no fixed decibel limit (Mo. Rev. Stat. § 307.170).
Verified Jun 19, 2026 · Source: revisor.mo.gov · Full Missouri rule →
WisconsinInfo
Your vehicle needs an adequate muffler operating at all times, and cutouts and bypasses (which route exhaust around the muffler) are prohibited, along with changes that amplify noise beyond the factory muffler. Wisconsin sets no fixed decibel limit (Wis. Stat. § 347.39).
Verified Jun 19, 2026 · Source: docs.legis.wisconsin.gov · Full Wisconsin rule →

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