What Is the Clean Truck Check? California’s New HD I/M Program Explained
California’s transportation regulations just got stricter — and if you operate diesel trucks over 14,000 pounds, you’re directly affected. The Clean Truck Check, also known as the Heavy-Duty Inspection and Maintenance (HD I/M) Program, is the California Air Resources Board’s (CARB) newest compliance program aimed at reducing pollution from heavy-duty vehicles.
In this post, we’ll break down everything fleet managers, owner-operators, and businesses need to know — and how NorCal CARB Mobile can help you stay compliant with convenient, mobile HD I/M testing services.
What Is the Clean Truck Check?
The Clean Truck Check is CARB’s statewide emissions inspection program for non-gasoline heavy-duty vehicles with a GVWR over 14,000 pounds. Think of it as California’s version of a smog check — but for big rigs, box trucks, buses, and other diesel-powered commercial vehicles.
It ensures that heavy-duty trucks operating in California are properly maintained and not releasing excessive emissions, particularly particulate matter (PM) and NOx (nitrogen oxides) — two major contributors to air pollution.
Who Must Comply?
The program applies to:
Diesel trucks over 14,000 lbs GVWR
Alternative fuel and hybrid trucks (non-gasoline)
California-registered and out-of-state trucks operating in California
Single owner-operators and fleets alike
Whether your vehicle is based in Sacramento, San Jose, or out of state, if it’s working on California roads, it’s subject to HD I/M testing requirements.
What Does the Program Require?
There are three major components of Clean Truck Check compliance:
Vehicle Emissions Control Equipment Inspection
Testers verify that emission control systems (like diesel particulate filters and SCR systems) are properly installed and functioning.
SAE J1667 Smoke Opacity Test
This test measures the amount of visible smoke a vehicle emits — an indicator of poor combustion or equipment failure.
OBD Testing (for newer vehicles)
Vehicles with onboard diagnostic systems must pass periodic digital scans.
When and How Often Do You Need to Test?
Testing frequency depends on vehicle model year and registration status. Most vehicles will need semi-annual testing, with additional roadside or surprise inspections possible.
Avoiding or delaying testing can lead to fines, registration blocks, or DMV holds.
Why Mobile HD I/M Testing Makes Sense
At NorCal CARB Mobile, we take the hassle out of compliance. No waiting in line at a test facility or taking vehicles out of service. Our mobile CARB-certified testers come to your location—whether it’s a fleet yard, construction site, or your driveway.
We serve:
Sacramento County
San Francisco Bay Area
San Diego County
Orange County
… and everywhere in between!
What Makes NorCal CARB Mobile Different?
✅ On-site smoke opacity and emissions control inspections
✅ CARB-certified technicians
✅ Fast scheduling and digital compliance reporting
✅ Transparent pricing with no surprise fees
✅ Fleet testing and single vehicle testing available
Ready to Schedule Your Clean Truck Check?
Don’t wait until you’re out of compliance. Call NorCal CARB Mobile or book online to schedule your mobile HD I/M test today.
📍 Serving California diesel truck operators statewide
NorCal CARB Mobile — Helping California fleets stay compliant, one truck at a time.
