Clean Truck Check is the California Air Resources Board’s heavy-duty inspection and maintenance program. It goes beyond the old “smoke check only” approach with periodic testing that confirms a truck’s emissions-control system is working, and gets it repaired if it is not. To comply, owners generally need to:
Report each vehicle in CARB’s CTC-VIS system and pay the annual compliance fee.
Pass periodic emissions tests performed by a credentialed tester with CARB-verified equipment.
Repair any emissions-control problems and pass a retest when a truck fails.
Clean Truck Check and the 14,000 lbs GVWR threshold
The program covers most diesel and alternative-fuel vehicles with a gross vehicle weight rating over 14,000 lbs that operate in California. Some vehicles, such as certain emergency and military vehicles, are exempt.
Clean Truck Check for out-of-state trucks
Trucks registered in other states or in Mexico are covered when they drive in California. Out-of-state carriers also report their vehicles in CTC-VIS and keep testing up to date. We test out-of-state trucks anywhere in Southern California, including at the ports.
Which test does my truck need?
The test depends on the engine model year and whether it has on-board diagnostics. See our CARB OBD test and smoke opacity test pages.
Vehicle → test method
2013+ diesel engines with OBD
CARB-verified OBD test
2012 and older diesel without OBD
Smoke opacity test + visual inspection
2018+ alternative-fuel engines with OBD
CARB-verified OBD test
2017 and older alternative-fuel without OBD
Visual inspection
Clean Truck Check test method by vehicle type
Vehicle
Test method
2013+ diesel engines with OBD
CARB-verified OBD test
2012 and older diesel without OBD
Smoke opacity test + visual inspection
2018+ alternative-fuel engines with OBD
CARB-verified OBD test
2017 and older alternative-fuel without OBD
Visual inspection
Most covered trucks (over 14,000 lb GVWR, including out-of-state trucks driving in California) currently test twice a year. Under the original rule, OBD-equipped vehicles move to four tests per year from October 1, 2027. A bill has proposed cutting testing to once a year, so requirements may change. Always check your own deadlines in CARB’s CTC-VIS system. Open CTC-VIS Source: California Air Resources Board.
Clean Truck Check deadline and testing frequency
Most covered trucks (over 14,000 lb GVWR, including out-of-state trucks driving in California) currently test twice a year. Under the original rule, OBD-equipped vehicles move to four tests per year from October 1, 2027. A bill has proposed cutting testing to once a year, so requirements may change. Always check your own deadlines in CARB’s CTC-VIS system.
Clean Truck Check 2027 quarterly testing
Under the original rule, OBD-equipped vehicles move from twice-a-year testing to four tests a year (quarterly) starting October 1, 2027. Because proposed legislation could change testing frequency, check CARB’s official pages and your CTC-VIS account before planning your schedule. Diesel Dynamix can set up recurring fleet visits that follow whatever schedule applies.
CTC-VIS registration
CTC-VIS (Clean Truck Check Vehicle Inspection System) is where you report vehicles, pay the annual compliance fee and see each truck’s deadlines. Open CTC-VIS.
Clean Truck Check fines, penalties and DMV registration holds
Trucks that are out of compliance can face DMV registration holds for California-registered vehicles, plus citations and penalties set by CARB. Amounts and procedures can change, so rely on CARB for current figures. The simplest protection is testing on time. See why California enforces it.
Clean Truck Check is the public name for CARB's heavy duty inspection and maintenance regulation, often called the HD I/M regulation. The California Clean Truck Check law covers most diesel and alternative-fuel vehicles over 14,000 lb GVWR that operate in the state, whether they are registered in California, another state or another country.
The idea is simple. Trucks are built with emissions controls, and this regulation checks that those controls still work out on the road. That is why the test looks at the engine's OBD data on newer trucks, and at smoke and visible equipment on older ones.
Clean Truck Check covers tractor trailers, but it also covers much more. Box trucks, dump trucks, buses, refuse trucks, construction and agricultural vehicles and motorhomes over 14,000 lb can all be part of the CARB heavy duty vehicle inspection program. Edge cases exist, so check CARB's rules for your vehicle.
When is my Clean Truck Check due? Finding your deadline
Your Clean Truck Check deadline is listed for each vehicle in CARB's CTC-VIS system. That is the one place for a Clean Truck Check deadline lookup, because deadlines are set per vehicle rather than one date for everyone.
A few practical tips:
Log in to CTC-VIS and check each VIN. If a vehicle is missing, it needs to be added before it can show as compliant. Our CTC-VIS registration guide walks through it.
Book ahead of the date, not on it. A failed test means repair and a retest, and that takes time.
Keep a calendar for every truck. With most vehicles testing twice a year, a small fleet quickly has a lot of dates.
When we test your truck, we give you the next due date and can send a reminder before it arrives. Fleets can set up recurring visits so nobody has to track the dates by hand.
Clean Truck Check compliance fee vs. the testing fee
There are two separate costs in Clean Truck Check: CARB's annual compliance fee and the testing fee. They go to different places and are paid in different ways.
The compliance fee is set by CARB and charged per vehicle each year. You pay it in CTC-VIS, where the current amount is shown. It is the same no matter which tester you use.
The testing fee is what the tester charges to perform the test. Ours depends on how many trucks we test, the test type and your location, with per-truck pricing for fleets.
Paying one does not cover the other. A truck can pass its test and still not be compliant if the annual fee is unpaid, and paying the fee does not replace the test.
Clean Truck Check exemptions: check before you assume
Some vehicles fall outside Clean Truck Check or follow special rules, but the details are set by CARB and they matter. Do not assume a vehicle belongs on the list of Clean Truck Check exempt vehicles, and do not assume a truck is exempt because it is new, used rarely or owned by a farm or public agency.
The safest path is:
Confirm the GVWR. The program is aimed at vehicles over 14,000 lb.
Confirm the fuel. It covers diesel and alternative-fuel engines.
Check CARB's rules for your vehicle, or ask CARB directly, if you think an exemption applies.
Guessing wrong is costly. A California-registered vehicle that should have tested can end up with a DMV registration hold, and CARB can issue citations and penalties.
Still unsure? Call or text (858) 342-8328 and we will help.
When is my Clean Truck Check due?
Each vehicle's Clean Truck Check deadline is shown in CARB's CTC-VIS system. When we test your truck, we also give you the next due date and can send a reminder before it.
What are the Clean Truck Check 2026 requirements?
In 2026, owners report each vehicle in CTC-VIS, pay CARB's annual compliance fee and pass periodic emissions tests. Most covered vehicles currently test twice a year.
Will Clean Truck Check move to quarterly testing in 2027?
Under CARB's original rule, OBD-equipped vehicles move to four tests per year starting October 1, 2027. A bill has proposed cutting testing to once a year, so the schedule may change.
Is there a Clean Truck Check annual fee?
Yes. CARB charges an annual compliance fee per vehicle, paid in CTC-VIS, where the amount is shown. It is separate from the fee the tester charges for the test.
Can an out-of-state truck get a Clean Truck Check citation?
Yes. Clean Truck Check covers interstate trucks, including out-of-state and international trucks that operate in California, and CARB can issue citations and penalties to vehicles that are not compliant.
Are any vehicles exempt from Clean Truck Check?
Some vehicles are exempt or follow special rules, but CARB sets those details. Check CARB's rules for your vehicle before assuming it does not need to test.
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