Napa's Mobile Diesel Smog Check & Clean Truck Check — Done Right, On Your Schedule

A Clean Truck Check is a CARB-mandated diesel emissions test required for all commercial vehicles with a gross vehicle weight rating (GVWR) of 14,000 pounds or more operating in California. If you own or operate diesel trucks in Napa County, Sonoma County, or anywhere in California, you are required to pass this test to stay compliant. Non-compliant vehicles face fines up to $10,000 per vehicle per day and DMV registration holds.

As of 2026, most diesel vehicles require semi-annual testing — that means twice per year. Starting in October 2027, CARB is increasing the requirement to quarterly testing (four times per year) for OBD-equipped vehicles. Staying on top of your schedule now prevents costly penalties and registration blocks down the road.

You don't need to go anywhere — we come to you. Ramos NorCal Diesel Smog provides mobile CARB-certified testing throughout Napa, Sonoma, American Canyon, Benicia, Yountville, Rutherford, Saint Helena, Calistoga, and surrounding North Bay areas. We test at your job site, yard, or wherever your trucks are parked.

Our first truck is $110 (includes a $30 travel fee plus $80 for testing). Each additional truck during the same visit is $80. For fleets of 3 or more trucks, the travel fee is waived — so every truck is just $80. No hidden fees, no surprises.

A typical Clean Truck Check inspection takes 15 to 20 minutes per vehicle. We arrive on time, perform the test on-site, and you receive your certification immediately. Most fleet visits are completed within a few hours depending on the number of trucks.

If a vehicle doesn't pass, we'll explain exactly what the issue is and what repairs are needed to bring it into compliance. Once repairs are completed, we can return to retest. It's important to address failures promptly — vehicles that miss their compliance deadline can face fines and DMV registration holds.

Yes. Diesel-powered motorhomes and recreational vehicles with a GVWR of 14,000 pounds or more are subject to Clean Truck Check requirements. We test RVs throughout Napa and Sonoma County — we'll come right to your home or storage location.

CARB can impose fines up to $10,000 per vehicle per day for non-compliance. Your vehicle's DMV registration can also be blocked until the issue is resolved, and out-of-state trucks may be restricted from operating in California. The compliance fee for 2026 is $32.13 per vehicle — a small price compared to the penalties.

Yes — the fee covers the emissions inspection itself, whether your vehicle passes or fails. Running the test is the service, and a failed result tells you exactly what needs attention before your compliance deadline. If your truck doesn't pass, you'll receive a full diagnostic summary of what needs to be addressed, plus a complimentary re-test within 30 days once the repair is complete.