California Heavy-Duty Inspection & Maintenance Program

Clean Truck Check (CTC) is California’s heavy-duty inspection and maintenance program, designed to identify and reduce excess emissions from in-use trucks operating on public roads. It applies to most diesel and non-zero-emission vehicles over 14,000 lbs GVWR that operate in California, including vehicles registered out of state. Covered vehicles must be reported to CARB, pay an annual compliance fee, and submit passing emissions tests on a recurring schedule, including additional testing when required through Notices to Submit to Testing (NSTs).

CTC generally applies to:

  • Diesel and non-zero-emission vehicles over 14,000 lbs GVWR
  • Trucks registered inside or outside California if they operate on CA public roads
  • Commercial, private, and government fleets

CTC does not apply to:

  • Zero-emission vehicles
  • Military tactical vehicles
  • Emergency response vehicles
  • Historical vehicles (as defined by CA Vehicle Code)
  • Certain motorhomes used only for recreation
  • Engines certified to CARB’s optional low-NOx standard (exempt until Jan 1, 2027)

What Fleets Must Do to Comply

Register vehicles

Fleets must report covered vehicles in CARB’s Clean Truck Check Vehicle Inspection System (CTC-VIS). Welcome – CTC-VIS

Pay annual compliance fees

An annual fee applies per vehicle and must be paid to remain compliant.

Complete emissions testing

Vehicles must undergo emissions testing at the required frequency, which is generally twice per year, and quarterly for certain OBD-equipped vehicles (beginning in October 2027) using either:

  • CARB-credentialed testers
  • CARB-approved testing devices

Submit passing test results

Passing results must be uploaded to CTC-VIS by the applicable deadline.

Conduct further testing when notified

Fleets must complete and submit additional emissions testing by the specified deadline when CARB issues a Notice to Submit to Testing (NST). This testing is in addition to the regularly required testing.

Enforcement

CARB enforces CTC using:

  • Roadside emissions monitoring (REM)

REM is a roadside screening method CARB uses to identify potentially high-emitting heavy-duty vehicles while they are operating (without stopping the truck). If emissions exceed CARB thresholds, CARB may issue a Notice to Submit to Testing (NST).

  • Automated license plate recognition
  • Database-driven compliance checks

Consequences of non-compliance may include:

  • Notices requiring immediate testing
  • DMV registration holds
  • Fines or operational restrictions

Why Clean Truck Check Matters

CTC replaces older opacity-based exhaust testing programs and focuses on identifying high-emitting vehicles throughout the year and not just at registration renewal. The program is designed to reduce NOx and particulate matter emissions from heavy-duty trucks operating in California. 

Clean Truck Check – Fact Sheets, Guides & Videos | California Air Resources Board

This page provides general information about California’s Clean Truck Check program and is intended for educational purposes only. Program requirements, deadlines, exemptions, and enforcement practices are determined by the California Air Resources Board (CARB) and may change. Fleets should consult CARB’s official Clean Truck Check resources for the most current and authoritative information.