CARB Clean Truck Check Question and Answers
Q: What is a CARB mobile test?
A: An on-site inspection and emissions test performed to California Air Resources Board standards — we bring certified equipment and handle required paperwork.
Q: Which vehicles do you test?
A: Fleets, trucks, motorhomes, and other qualifying over 14k lbs. diesel vehicles — we service California- at your location.
Q: How long does an on-site test take?
A: Most inspections take 10-30 minutes depending on vehicle type and paperwork.
Q: Do you handle CARB paperwork/submission?
A: Yes — we document, submit, and provide proof of compliance to reduce your administrative burden.
Q: How do I book?
A: Book online, call our office 916-890-4427, or use the chatbot to schedule. We’ll confirm time, cost, and required documents.
CARB Clean Truck Glossary
(customer-friendly)
CARB — California Air Resources Board
The state agency that sets air-quality and emissions rules in California. If you hear “CARB,” it’s about California rules for keeping the air clean.
Clean Truck Check (CTC)
A common name for an on-site emissions inspection and paperwork process that makes sure a truck or motorhome meets CARB rules. (At NorCal CARB Mobile, this is the service we perform at your location.)
Clean Truck Check — J / SAE J1667
Often written “CTC-J” or “J1667.” This is a specific type of smoke test (the “snap-acceleration” smoke test) used to measure visible diesel smoke during a quick acceleration. It’s a standard test method used in many mobile inspections.
On-Board Diagnostics (OBD)
The vehicle’s onboard computer system that monitors engine and emissions components. If the OBD system detects a problem, it often lights up the “Check Engine” lamp.
OBDII / HD-OBD
Different OBD generations and standards. “OBDII” is common on many light vehicles; heavy-duty trucks use different/advanced OBD systems. In all cases, OBD gives us information about engine faults and emissions systems.
Check Engine Light / MIL (Malfunction Indicator Lamp)
The dashboard light that tells you the vehicle’s computer has detected an emissions or engine problem. A lit MIL usually needs diagnosis and repair before a passable emissions test.
VIN — Vehicle Identification Number
The unique 17-character ID for your vehicle. Technicians use this to pull up vehicle history and match paperwork.
GVWR — Gross Vehicle Weight Rating
The manufacturer’s maximum weight rating for a vehicle when fully loaded. GVWR helps determine what class a vehicle is and which tests or rules apply.
Vehicle Class (Light / Medium / Heavy Duty)
Vehicles are grouped by weight and use. A vehicle’s class affects which CARB rules and tests it needs. Commercial trucks are typically medium or heavy duty.
DPF — Diesel Particulate Filter
A filter installed on many diesel vehicles that traps soot (particulate matter). A missing or tampered DPF usually causes a failed emission test.
SCR — Selective Catalytic Reduction
An emissions system that reduces NOx (nitrogen oxides) using a catalyst and a liquid called DEF. Proper SCR operation is important for meeting NOx limits.
DEF — Diesel Exhaust Fluid
A liquid used by SCR systems to reduce NOx. If DEF is empty or the SCR is not working, the vehicle may fail emission checks.
NOx — Nitrogen Oxides
Pollutant gases from diesel engines that contribute to smog and respiratory problems. CARB regulations focus heavily on reducing NOx from trucks.
PM — Particulate Matter
Tiny solid particles (soot) from diesel exhaust that can affect air quality and health. DPFs reduce PM emissions.
Opacity
A measurement of how much smoke or soot blocks light from exhaust. Opacity meters measure visible smoke during certain tests (like J1667).
Opacimeter
The tool used to measure exhaust opacity (how “thick” the smoke is). It gives a number technicians use to decide pass/fail for smoke tests.
Smoke Test
A test that checks how much visible smoke the engine produces (often measured as opacity). Many diesel tests include a smoke check.
Retrofit / Retrofit Device
An aftermarket device (for example, a DPF or SCR) added to an older vehicle to reduce emissions and help it comply with CARB rules.
CARB Executive Order (EO)
A CARB-issued approval document. Many approved retrofit devices and parts carry an EO number showing CARB has certified that device for use.
Certified Technician / CARB-certified Tester
A technician who is trained and authorized to perform CARB tests and sign the official paperwork.
Equipment Calibration
Emission-testing instruments must be checked and calibrated regularly so test results are accurate. Technicians will note calibration status on inspections.
Proof of Compliance / Certificate of Compliance
The paperwork or digital proof you receive after a successful test. Keep this for your records or fleet paperwork.
Failure / Repair Order
If a vehicle fails a test, you’ll receive a failure notice. The vehicle must be repaired and then retested (a “re-test”) to show it meets the requirements.
Re-test
A repeat test after repairs. Depending on the program, re-tests may be free within a certain window or may carry a separate fee.
Exemption
Under limited circumstances a vehicle may be temporarily or permanently exempt from a specific CARB requirement. Exemptions are specific and documented; ask us or CARB for details that apply to your vehicle.
Fleet Compliance Plan
A written plan a fleet may use to schedule tests, repairs, and recordkeeping to keep all vehicles compliant with CARB rules.
On-site / Mobile Testing
A service where a certified technician brings equipment to your location (yard, depot, job site) to perform CARB inspections — the type of service NorCal CARB Mobile provides.
Appointment / No-show / Cancellation Policy
Common operational terms: customers should arrive on time and provide accurate vehicle info. Missed appointments or late cancellations may incur fees; check the service provider’s policy.
Enforcement & Fines
CARB has enforcement measures that can include fines for non-compliance. Staying current with testing and paperwork helps avoid penalties and business interruptions.
EPA / DOT / DMV
Other agencies you may hear about: EPA (U.S. Environmental Protection Agency), DOT (Department of Transportation), and DMV (Department of Motor Vehicles). CARB rules interact with federal and state agencies in various ways.
Quick tips customers should know
Bring paperwork & VIN: Have vehicle registration, VIN, and any prior CARB docs available.
Fix obvious faults: A lit check engine light, missing emission parts (like a DPF), or low DEF are common fail reasons.
Plan for downtime: Tests typically take 30–90 minutes; repairs and re-tests take longer.
Keep records: Keep your Certificate of Compliance and repair receipts handy for audits or fleet records.
Ask for EO numbers: If a retrofit was installed, the EO number shows CARB approval for that device.