Compliance Resource
Diesel Truck and Fleet Compliance FAQ: California 2026 to 2027
California has the toughest diesel truck rules in the country, and they keep changing. Fleet managers and owner operators ask us the same questions every week: When is my Clean Truck Check due? Is Advanced Clean Fleets still happening? Why is my truck derating? What will the CHP look at during a BIT inspection?
We put the answers in one place. This page covers CARB emissions rules, DOT and BIT inspections, DPF, EGR and DEF problems, and what is changing in 2026 and 2027. If your truck or fleet runs in Ontario, Rancho Cucamonga, Fontana, Upland, Chino, Pomona or anywhere in the Inland Empire, Rapid Diesel Repair can help you stay compliant and on the road.
Last updated: September 2026. Rules change often. We review this page regularly, but always confirm your specific situation with CARB, the CHP or FMCSA.
Rapid Diesel Repair is a diesel repair and compliance service shop. We are not attorneys and nothing on this page is legal advice. Where a question touches on legal obligations, penalties or enforcement, we share what we have seen in our shop and what the agencies have published. For legal advice about your business, talk to a qualified transportation or environmental attorney.
Quick Answers
What compliance does a diesel truck need to run in California?
Most heavy-duty diesel trucks over 14,000 lbs GVWR need four things: a 2010 or newer engine (CARB Truck and Bus Regulation), a current Clean Truck Check (CARB emissions testing and annual fee), a DOT annual inspection, and, for many fleets, CHP BIT 90-day inspections. Refrigerated units, port drayage trucks and some fleets have extra rules. Rapid Diesel Repair in Ontario handles CARB, DOT and BIT compliance under one roof.
What is the Clean Truck Check?
Clean Truck Check is CARB's heavy-duty emissions inspection program, also called HD I/M. It requires most diesel and alternative-fuel trucks over 14,000 lbs GVWR to report the vehicle to CARB, pay an annual compliance fee and pass periodic emissions tests. It applies to California trucks and out-of-state trucks that drive on California roads.
How often do I need a Clean Truck Check test?
Most covered vehicles currently need two compliance tests each year. CARB schedules each vehicle's deadlines through the Clean Truck Check Vehicle Inspection System, so owners should use the dates shown in their own account rather than relying only on a general calendar. CARB says OBD equipped vehicles are scheduled to move to four tests per year beginning in October 2027, while qualifying agricultural vehicles and California registered noncommercial motorhomes remain annual. A passing result can generally be submitted up to 90 days before the deadline. Testing early leaves time to diagnose a fault, complete a repair, drive the vehicle until its readiness monitors run and submit a passing retest. Read our Clean Truck Check guide for the complete planning process.
How much is the Clean Truck Check fee?
CARB charges an annual compliance fee for each covered vehicle, and that fee is separate from what a credentialed tester charges to perform a compliance test. The state fee began at $30 and is adjusted for inflation, so owners should confirm the current amount inside CTC-VIS or on CARB's official website before paying. A diagnostic inspection, emissions repair, DPF cleaning and retesting can also be separate services. Ask for an itemized estimate so you understand which charge is the state fee, which is the official test and which work is repair or maintenance.
How often does a truck need a DOT annual inspection?
A commercial motor vehicle subject to 49 CFR 396.17 must pass a periodic inspection at least once every 12 months. The inspection must cover the required components and be completed by a qualified inspector. The carrier must keep the inspection report for 14 months from the report date, and the vehicle must carry or display evidence of the current inspection. The annual inspection is different from a driver's pretrip and post trip checks. California fleets may also have 90 day BIT inspection duties, so one annual inspection does not automatically replace every other maintenance and recordkeeping obligation.
What is a BIT inspection?
BIT stands for the California Highway Patrol Basic Inspection of Terminals program. It applies to specified motor carriers and vehicles, including many truck tractors, larger commercial trucks, regulated trailers and certain other vehicles listed in California law. Covered vehicles must receive documented safety inspections at least every 90 days, or more often when their condition or use requires it. Inspectors review items such as brakes, steering, suspension, tires, wheels, lighting and coupling equipment. The CHP can inspect the terminal's vehicles, maintenance files, driver records and proof that reported defects were repaired. Because applicability depends on vehicle type and operation, confirm your fleet's status with the CHP rather than assuming every truck follows the same rule.
Is a DPF delete legal in California?
No. Removing, bypassing or disabling a diesel particulate filter, EGR valve, SCR catalyst, DEF system or related emissions controls is unlawful under federal and California requirements. A tuner or software change that prevents the system from operating can also be considered tampering. A modified truck can fail inspection, receive an emissions compliance hold and expose the owner or installer to enforcement. Rapid Diesel Repair does not perform deletes. We diagnose the reason for repeated regeneration, derate or warning lights and repair the emissions system. Read our DPF cleaning and repair guide to understand why a filter may keep clogging and when cleaning alone is not enough.
Do you work on all truck brands?
Yes. Rapid Diesel Repair services Freightliner, Peterbilt, International, Hino, Isuzu, Dodge Ram, Sterling and more, plus Cummins, Detroit, PACCAR and Navistar engines and Allison transmissions.
CARB Clean Truck Check (HD I/M)
Which trucks need Clean Truck Check?
Nearly all diesel and alternative-fuel heavy-duty vehicles over 14,000 lbs GVWR that operate on California public roads. That includes out-of-state and Mexico-registered trucks. Exemptions include zero-emission vehicles, military tactical vehicles, emergency vehicles, historical vehicles and motorhomes registered outside California.
How is my Clean Truck Check deadline set?
For California-registered trucks, the deadline is tied to your DMV registration expiration date. For out-of-state trucks, it is based on the last digit of the VIN. You can see your exact deadlines in your CTC-VIS account on CARB's website.
How early can I test before my deadline?
You can test up to 90 days before your compliance deadline. We recommend testing 30 to 60 days early. That leaves time to fix a problem and retest without risking a registration hold.
What happens if I miss my Clean Truck Check deadline?
CARB can mark the vehicle noncompliant, and the California DMV may place a registration hold that prevents renewal. The vehicle may also be subject to enforcement while it remains out of compliance. A test appointment by itself does not clear the problem: the required fee must be paid, the vehicle must receive a valid passing result and the records must reach the state systems. If the truck fails, diagnose and repair the actual fault before retesting. CARB advises allowing processing time after payment and a passing result, so do not wait until the registration date to begin. Use our Clean Truck Check guide to organize the deadline, repair, readiness drive and retest.
What is the difference between an OBD test and a smoke test?
Diesel trucks with 2013 or newer engines (and alternative-fuel trucks with 2018 or newer engines) get an OBD test. The tester plugs into the truck's computer and CARB checks fault codes and readiness monitors. Older trucks get a smoke opacity test with an approved smoke meter plus a visual inspection of emissions equipment.
Why did my truck fail the OBD test with no check engine light on?
The warning light does not need to be illuminated for an OBD compliance result to fail or be rejected. The system may show incomplete readiness monitors, a stored or pending emissions code, a communication problem or evidence that codes were recently cleared. Disconnecting batteries or clearing codes shortly before testing can reset monitors without repairing the cause. The next step is to save the test report and diagnostic information, inspect the relevant circuit or emissions system, repair the verified fault and operate the truck under the conditions needed for its monitors to complete. Do not replace a NOx sensor, DPF component, DEF doser or EGR part based only on a code name. A code identifies the system that detected a problem, not always the failed part.
Can I clear the codes and then test?
No. CARB specifically warns not to test right after clearing codes. Clearing codes resets the readiness monitors, so the truck will likely fail. Drive the truck normally so the monitors can complete, or have the underlying problem repaired first.
My truck failed. What are the next steps?
Get the fault properly diagnosed and repaired, drive the truck enough for the monitors to reset, then retest before your deadline. Bring the failed test report to Rapid Diesel Repair in Ontario and we will use it to target the repair.
Can I do my own Clean Truck Check test?
Yes, if you complete CARB's free credentialed tester training, pass the exam with 80 percent or higher and use a CARB-approved OBD device. Many fleets find it easier to have a shop handle testing and repairs together.
What is the 5-day pass?
Out-of-state trucks that rarely come to California can use a five consecutive day pass once per calendar year. It must be submitted at least 7 business days before the truck enters California.
Can CARB flag my truck while it is driving?
Yes. CARB uses roadside remote emissions monitoring devices together with license plate readers to spot high-emitting trucks. A flagged truck gets a notice and 30 days to submit a passing test.
I bought a used truck. Who is responsible for Clean Truck Check?
CARB puts the responsibility on the buyer. Before you buy, check the truck's status and ask for a recent passing test. After purchase, update the truck in your CTC-VIS account. We also do pre-purchase inspections so you are not buying someone else's emissions problems. (Not legal advice. Confirm transfer rules with CARB.)
Does Clean Truck Check replace the smog check?
Clean Truck Check applies to heavy-duty trucks over 14,000 lbs GVWR. Light and medium-duty diesel pickups and vans under that weight still follow the regular California Smog Check program run by the Bureau of Automotive Repair.
Is the PSIP annual smoke test still required?
Fleets with two or more diesel vehicles over 6,000 lbs GVWR have long been required to do annual smoke tests under CARB's Periodic Smoke Inspection Program (PSIP). CARB has published guidance on how PSIP overlaps with Clean Truck Check. Check CARB's current guidance for your fleet, or ask us and we will walk you through it.
What are the penalties for Clean Truck Check violations?
According to CARB, violations of air pollution rules can carry civil penalties of $1,000 to $10,000 per day per vehicle, and tampering can reach up to $37,500 per violation. Actual amounts depend on the case. (Not legal advice. We are not attorneys. This is based on CARB's published information.)
What Is Changing in 2026 and 2027
Is Advanced Clean Fleets still happening?
For most private fleets, no. After federal waiver and legal challenges, CARB moved to formally repeal the Advanced Clean Fleets requirements for high-priority private fleets and drayage fleets, and filed the repeal in 2026. State and local government fleets still have zero-emission purchase requirements on a delayed timeline. Enforcement for private fleets was already paused. (Not legal advice. Check CARB for the final status of the repeal.)
Do drayage trucks still need to register for port access?
Yes. Even with the state ACF drayage rule being repealed, the Ports of Los Angeles and Long Beach still require trucks to be in the Port Drayage Truck Registry, and the Clean Truck Fund rate still applies to diesel trucks. Port programs are separate from CARB rules.
What is the EPA 2027 NOx rule?
It is the federal rule that sets much tighter NOx emissions limits for new heavy-duty engines starting with model year 2027. In July 2026, EPA proposed changes that keep the core NOx standard but ease other parts, such as warranty periods, longer useful-life requirements and DEF derates. It is a proposal, so final details can change.
Should I buy a new truck before 2027?
Many fleets are asking this. 2027 engines are expected to cost more and use new technology. Some fleets are buying 2026 model year trucks early, while others are waiting for EPA's final rule. It depends on your budget, trade cycle and routes. What we tell customers: whatever you run, a well-maintained emissions system matters more than the model year.
What changed with DEF derates?
In August 2025, EPA issued guidance so trucks do not lose power suddenly when the DEF system has a fault. For heavy-duty trucks, the new sequence is a warning for the first 650 miles or 10 hours, then a mild derate with no speed limit for a few weeks, and only after about four weeks a 25 mph limit. Engine makers including Daimler (Detroit) and PACCAR have released software updates for existing trucks.
Do I need the DEF software update?
If your truck has the older, harsher derate programming, the update can save you from being stuck on the side of the road. Ask us to check whether an update is available for your engine. It still does not replace fixing the DEF fault itself.
Did EPA remove the DEF sensor requirement?
In March 2026, EPA removed the requirement for the DEF quality (urea quality) sensor and allowed manufacturers to use NOx sensor based monitoring instead, through approved software updates. DEF, the SCR system and the DPF are all still required.
Are DPF and EGR deletes legal now?
No. In January 2026 the Department of Justice said it would stop pursuing criminal charges for OBD tampering, but deletes are still illegal under federal law and civil penalties still apply. California and CARB continue to enforce tampering rules, and a deleted truck cannot pass Clean Truck Check. (Not legal advice. We are not attorneys. This is what the agencies and news reports have published.)
Can I still buy a new truck in California if manufacturers are fighting CARB rules?
Yes. In 2025 CARB adopted emergency rules so manufacturers can certify new trucks to either the newer low-NOx Omnibus standards or the older standards. That kept new trucks available for sale in California while the legal fight continues.
Is the Truck and Bus Regulation still in effect?
Yes. Since January 1, 2023, almost all diesel trucks and buses over 14,000 lbs GVWR must have a 2010 or newer model year engine to operate in California. The DMV will not register non-compliant trucks. Some exemptions exist and must be reported to CARB.
Will Clean Truck Check testing go to four times a year?
Yes, that is the plan. Starting in October 2027, OBD-equipped heavy-duty trucks move to quarterly testing. Motorhomes and agricultural vehicles stay annual. Plan for twice as many tests per truck starting in late 2027 and build it into your PM schedule.
Did the EPA endangerment finding repeal or the SIP decision end Clean Truck Check?
No. CARB has stated that Clean Truck Check is not a greenhouse gas rule and remains fully in effect. A January 2026 EPA decision on California's air plan does not stop CARB from enforcing the program.
DPF, EGR, DEF and Emissions Repair
Why does my DPF keep clogging or regenerating too often?
Frequent regens usually point to an upstream problem, not just a dirty filter. Common causes are a leaking injector, EGR problems, a failing DPF pressure sensor, a bad DOC, excessive idling or short trips that never let the truck regen fully. Cleaning the filter without fixing the cause means it will clog again.
How often should a DPF be cleaned?
Most manufacturers recommend a professional DPF cleaning somewhere between 200,000 and 400,000 miles or 4,500 to 6,500 engine hours. Trucks that idle a lot, run short routes or do city delivery often need it sooner. We check your regen history and backpressure readings to tell you when it is actually due.
What is the difference between DPF cleaning and a forced regen?
A regen burns soot inside the filter using high exhaust heat. It does not remove ash. Ash builds up over time and can only be removed by taking the filter off and cleaning it professionally. If regens are not solving the problem, the filter likely needs a cleaning.
What are the signs of a bad EGR valve or cooler?
Loss of power, black smoke, rough idle, overheating, coolant loss with no visible leak and EGR fault codes. A leaking EGR cooler can push coolant into the intake and damage the engine, so do not ignore it.
Why is my truck in derate?
The most common causes are DEF quality or level faults, DEF doser or pump failure, NOx sensor failure, a clogged DPF, EGR faults or SCR efficiency codes. Each engine brand has its own patterns, so we read the actual codes and freeze-frame data before replacing parts.
My NOx sensor keeps failing. Why?
NOx sensors can fail from age and heat, but repeated failures often point to exhaust leaks, wiring damage, poor DEF quality or an upstream issue. We check the whole system so you are not buying sensors over and over.
Does DEF go bad?
Yes. DEF breaks down with heat and time. In hot Inland Empire summers, DEF stored in direct sun can degrade in months. Buy from high-turnover suppliers, keep it out of the sun and never top it off with water or anything else.
Will a repaired emissions system pass Clean Truck Check?
A properly repaired system with all monitors complete should pass. We recommend driving normally for a few days after major repairs so readiness monitors can run, then testing. We can test and repair in the same visit when it makes sense.
DOT Annual Inspections and CHP BIT
Who can perform a DOT annual inspection?
A qualified inspector as defined in 49 CFR 396.19. That means someone with training or experience, such as a mechanic who understands the inspection standards and can identify defective parts. The carrier must keep proof of the inspector's qualifications.
What gets checked in a DOT annual inspection?
Brakes, steering, suspension, tires, wheels and rims, lighting, frame, fuel system, exhaust, coupling devices, windshield and wipers, and other safety items listed in Appendix G of the federal regulations.
Which vehicles are in the BIT program?
Under California Vehicle Code 34500, BIT covers trucks with three or more axles over 10,000 lbs GVWR, truck tractors, trailers and dollies pulled by them, combinations over 40 feet, commercial vehicles over 26,000 lbs GVWR, placarded hazmat vehicles and certain other regulated trucks.
How often do BIT trucks need to be inspected?
Every regulated vehicle must be inspected at least every 90 days, or more often if needed. Not 91 days. Records must be kept for at least two years.
How does the CHP decide which terminals to inspect?
Since 2016, BIT inspections are performance based. The CHP uses a California Performance Safety Score built from federal safety data. Carriers with high scores, terminals never inspected before and hazmat terminals are more likely to be selected.
What are the most common reasons fleets fail a BIT inspection?
From what we see and what CHP reports show: brakes out of adjustment, missed or late 90-day inspections, defects written on driver inspection reports that were never repaired, new drivers not enrolled in the DMV Pull Notice program, and incomplete maintenance records. Most of these are paperwork and scheduling problems that are easy to prevent.
What happens if I fail a BIT inspection?
An unsatisfactory rating can lead to follow-up inspections and can put your Motor Carrier Permit at risk. It can also affect insurance rates and customer contracts. (Not legal advice. We are not attorneys. This is what we have seen with fleets we work with.)
Can Rapid Diesel Repair handle our 90-day BIT inspections?
Yes. We perform 90-day BIT inspections on trucks and trailers, fix what we find and give you clean, organized inspection records so your file is ready when the CHP shows up. We can also schedule your fleet so nothing goes past 90 days.
Does a DOT annual inspection count as a BIT inspection?
A thorough inspection can meet both requirements if it covers everything required and is documented correctly. We can combine them to save downtime. Ask us how we set this up for fleets in Ontario and the Inland Empire.
Roadside Inspections and Federal Rules
What did CVSA focus on in 2026?
International Roadcheck 2026 focused on ELDs and cargo securement. Brake Safety Week 2026 ran August 23 to 29 and focused on brake drums and air disc brake rotors. In 2025, about 15 percent of inspected vehicles were put out of service for brake problems during Brake Safety Week.
What are the most common out-of-service violations?
Brakes out of adjustment, brake system defects, tires, lighting and cargo securement are consistently at the top. Regular PM inspections catch most of these before a roadside inspector does.
Is English language proficiency an out-of-service violation now?
Yes. Since mid-2025, drivers who cannot communicate adequately in English during a roadside inspection can be placed out of service under federal rules. (Not legal advice. This is based on FMCSA's published enforcement guidance.)
My ELD was removed from the FMCSA list. What do I do?
FMCSA revokes ELDs that fail to meet requirements. Carriers get a limited window to switch to a registered device, and running a revoked ELD after that window can put the driver out of service. Check FMCSA's registered ELD list and replace the device promptly.
Special Equipment and Other California Rules
What are the rules for reefers (TRUs)?
Diesel transport refrigeration units that operate in California must be registered with CARB through the ARBER system, receive a CARB ID number and carry a valid compliance label. Large warehouses, grocery distribution centers, ports and railyards must also report or verify TRU compliance, and CARB has increased enforcement in 2025 and 2026.
How long can a diesel truck idle in California?
Generally no more than five minutes at any location under CARB's idling rule. Newer engines often have automatic shutdown or a clean idle certification. Excessive idling also causes more DPF and EGR problems, so it costs you in repairs too.
Do out-of-state trucks need to follow California rules?
Yes. Any truck operating on California roads must meet the Truck and Bus Regulation and Clean Truck Check, including reporting, fees and testing, no matter where it is registered.
Working With Rapid Diesel Repair
Where are you located and what areas do you serve?
Rapid Diesel Repair is located at 251 Kettering Dr, Ontario, CA 91761. We serve fleets and owner-operators within about 25 miles, including Ontario, Rancho Cucamonga, Upland, Chino, Fontana, Pomona, Montclair, Chino Hills, Eastvale, Jurupa Valley, Rialto and the greater Inland Empire.
What compliance services do you offer?
CARB Clean Truck Check testing and emissions repair, DOT annual inspections, CHP BIT 90-day inspections, DPF cleaning and repair, EGR and DEF/SCR repair, brake inspections and repair, and fleet preventive maintenance.
Do you offer fleet maintenance programs?
Yes. We build PM schedules around your Clean Truck Check deadlines, DOT annual dates and BIT 90-day cycles so testing and maintenance happen together and your trucks spend less time off the road.
Can you help if my truck already has a DMV registration hold?
Yes. We diagnose why the truck is non-compliant, make the repairs, get a passing test and help you understand what still needs to be done in your CTC-VIS account to clear the hold.
How do I schedule service?
Call us at 909-701-8755 or request service online. Tell us your truck's year, make, engine and what is going on, plus any compliance deadlines coming up, and we will get you in as fast as possible. Call to action block: Compliance deadline coming up? Truck in derate? Don't wait for a registration hold or a roadside inspection. Call Rapid Diesel Repair at 909-701-8755 or request service online. Serving Ontario, Rancho Cucamonga, Fontana, Upland, Chino, Pomona and the Inland Empire. > Disclaimer: The information on this page is general information based on our experience as a diesel repair shop and on information published by CARB, the CHP, EPA, FMCSA and industry sources. We are not attorneys and this is not legal advice. Regulations change often, so confirm current requirements with the responsible agency or a qualified attorney before making compliance or legal decisions.
Compliance Deadline Coming Up?
Truck in derate? Do not wait for a registration hold or roadside inspection. Serving Ontario, Rancho Cucamonga, Fontana, Upland, Chino, Pomona and the Inland Empire.