Clean Truck Check: A guide to California's compliance requirements

Heavy-duty vehicles make up only 3% of vehicles on California roads, yet they contribute to over 50% Open in new window of smog-causing pollution. The California Clean Truck Check requires that any fleet that operates heavy-duty trucks in the state must periodically test applicable vehicles for emissions and report the data to the California Air Resources Board (CARB) Open in new window. This includes trucks based in California and out-of-state trucks in California. 

Fleets that don’t comply with the CARB state requirements face fines of up to $10,000 per vehicle per day Open in new window, and out-of-state trucks may be restricted from operating in California.

This guide covers who must comply, how to register, what testing looks like and the deadlines fleet managers need to track.

What is the Clean Truck Check program?

The Clean Truck Check, also known as the Heavy-Duty Inspection and Maintenance (HD I/M) Program, is a California Air Resources Board (CARB) initiative designed to reduce emissions from heavy-duty vehicles. It requires fleet operators to:

• Register their vehicles with CARB
• Conduct regular emissions tests
• Submit emissions data for compliance verification

The Clean Truck Check aims to help fleets identify high-emitting trucks so they can repair malfunctioning vehicle systems and reduce their emissions. Although heavy-duty vehicles only make up 3% of the vehicles on the state’s roads, they are responsible for over half of the smog-causing pollution and fine particulate matter from vehicles. 

As of 2026, CARB requirements Open in new window apply to qualifying vehicles operating in California, including vehicles registered outside the state.

Who needs to comply with Clean Truck Check?

Clean Truck Check generally applies to heavy-duty vehicles with a GVWR over 14,000 pounds that operate in California, including qualifying vehicles registered outside the state. Fleets based outside California must also meet applicable requirements when their qualifying vehicles operate in the state. 

While the Clean Truck Check program mandates emissions testing for the majority of heavy-duty vehicles, specific categories are exempt, including:

• Zero-emissions vehicles
• Authorized emergency vehicles
• Military tactical vehicles
• Motorhomes registered outside of California
• Historical vehicles
• Vehicles operating under an experimental permit
• Gasoline vehicles
• New vehicles with engines certified to the most stringent optional NOx emissions standard

Carefully review the California BAR requirements for background on how California enforces vehicle emissions rules more broadly, including a related continuous testing program for government fleets. 

What are the Clean Truck Check requirements?

Meeting Clean Truck Check requirements involves registering applicable vehicles, completing emissions testing by the required deadlines, and maintaining compliance as testing cycles recur. The sections below walk through what each step involves in more detail. 

Register in the Clean Truck Check system

Fleets register applicable vehicles through the Clean Truck Check Vehicle Inspection System, known as CTC-VIS. From the CTC-VIS portal, fleet managers can add vehicles, pay the annual compliance fee and monitor compliance information and deadlines.

Keeping login access current across a compliance team helps avoid missed registration windows, particularly for larger fleets that add or retire vehicles throughout the year. 

Complete emissions testing

After registration, vehicles must complete the required emissions test within the applicable window and submit results to CARB. Many qualifying heavy-duty vehicles require testing twice per year, although schedules vary by vehicle. Fleets that miss a testing deadline risk fines and may face a DMV registration hold. 

Pro tip: Build testing into your regular maintenance schedule. Schedule Clean Truck Check testing with planned maintenance when possible. This can make it easier to address emissions-related issues before the testing deadline and reduce the risk of taking a vehicle out of service unexpectedly.

Maintain ongoing compliance

Clean Truck Check compliance does not end after the first passing test. Applicable vehicles must be retested according to CARB's recurring testing schedule, with deadlines based on factors like DMV registration or VIN for out-of-state vehicles.

Keeping vehicles well-maintained and between test dates reduces the chance of a failed test and the repair delays that follow. A Clean Truck Check certificate is issued after a passing test and should be kept accessible in the vehicles. 

How are Clean Truck Check tests done?

The testing method depends on the vehicle model year and equipment. The sections below explain when each testing method applies and what fleet operators need to know. 

OBD testing

Most heavy-duty vehicles built in recent model years use onboard diagnostics (OBD) to continuously monitor emissions-related systems.

For Clean Truck Check testing, fleets can upload data through a certified OBD scan tool or transmit it automatically by a connected vehicle telematics device, which removes the need for manual testing. 

Smoke opacity testing

Vehicles with engines built before the OBD requirement generally undergo smoke opacity testing instead. This test measures the visibility density of exhaust smoke and is paired with a visual inspection of emissions-related components. A credential tester, an individual authorized to perform inspections, performs both parts of the inspection. 

Roadside emissions screening

CARB also uses roadside tools, including Portable Emissions Acquisition Systems (PEAQS), to screen emissions from passing vehicles without stopping traffic.

If a vehicle appears to be a high emitter during roadside screening, CARB may issue a Notice to Submit to Testing Open in new window, which requires the fleet to complete a full test within a set timeframe. 

Why does Clean Truck Check matter?

The Clean Truck Check program exists to reduce harmful emissions from the vehicles responsible for the majority of smog-forming pollution on California roads, but compliance also directly benefits fleets.

Clean Truck Check is a separate program from routine smog check requirements that apply to light-duty vehicles. However both share the same larger goal of cleaner air across the state: 

• Reduces harmful emissions and supports cleaner air across the state
• Helps fleets avoid fines and registration holds
• Minimizes vehicle downtime by catching emissions issues early
• Supports better overall fleet maintenance and uptime
• Helps fleets prepare for expanding emissions testing requirements, including Clean Truck Check California rules that may extend to more vehicle types over time

How telematics helps streamline CARB compliance

Geotab's CARB-certified Clean Truck Check solution enables fleets operating in and driving through California to seamlessly comply with the state's environmental regulations. The solution supports both J1939 and J1979 protocols Open in new window and offers multiple installation options for continuous emissions data collection.

Automate emissions reporting

A connected telematics device can automatically generate and submit CARB-compliant emissions reports on schedule, which removes a significant piece of manual administrative work from the compliance process. 

Fleet managers also get advance notice as reporting deadlines approach rather than tracking dates manually across a spreadsheet. 

Monitor vehicle health

Beyond reporting, telematics data helps fleet managers track vehicles' overall performance. Telematics can alert fleet managers to diagnostic trouble codes and emissions-related faults. 

Essentially, this gives maintenance teams an opportunity to investigate and address issues before they contribute to a failed test or unexpected downtime. 

Reduce downtime and administrative work

Automated data collection can reduce the need to schedule separate testing appointments, helping fleets minimize administrative work and keep vehicles in service. This also means fleet managers do not need to manage Clean Truck Check compliance on a separate platform from the rest of their fleet operations. 

The MyGeotab platform can also help fleets reduce costs by identifying and reducing idling, optimizing routes, proactively managing fleet maintenance and more.

Streamline CARB compliance with certified technology

The CARB Clean Truck Check program requires heavy-duty vehicles operating in CARB states like California to undergo semi-annual emissions testing and reporting. Non-compliance can result in significant financial penalties and may even prevent out-of-state trucks in California from operating. 

To meet these requirements, fleets can utilize various methods, including certified testing facilities, portable emissions systems and telematics devices. Geotab’s CARB-compliant GO9 family of devices can automatically collect the required emissions data from vehicles and submit it to CARB, eliminating manual emissions testing and maximizing vehicle uptime.