Not all trucks have modern OBD systems. For older and certain heavy-duty vehicles, California’s emissions program still relies on the tried-and-true smoke opacity test (along with a visual inspection). Our Smoke Opacity Testing service is geared toward diesel trucks with 2012 or older engines, as well as any heavy vehicles not equipped with OBD. We help owners of these vehicles meet their “Clean Truck Check” requirements by accurately measuring exhaust smoke and inspecting emission control devices.
In simple terms, a smoke opacity test measures how much soot or particulate matter is in your vehicle’s exhaust by determining how opaque (dark) the exhaust smoke is. The more soot in the exhaust, the higher the opacity percentage, and the more pollution the vehicle is emitting. California limits the allowable opacity based on engine model year and type – our job is to ensure your truck’s emissions fall under those limits.
We perform smoke tests using the SAE J1667 “snap acceleration” method, which is the standard procedure adopted by CARB for heavy-duty diesel opacity testing. Here’s how it works:
Setup: We place an opacity meter (smoke meter) on your truck’s exhaust stack or tailpipe. This device has a light source and sensor to detect the density of smoke when the truck is revved.
Snap Acceleration Test: With the vehicle in neutral/park and at operating temperature, the inspector will rapidly press the accelerator (throttle) to run the engine up to governed high RPM, then release – this is one “snap.” We typically do a series of snaps (per the procedure) to get a stable reading. During each snap, the opacity meter measures the percentage of light blocked by the exhaust smoke plume.
Measurement: The peak opacity percentage from the test (or average of multiple readings) is recorded. For example, an older truck might have a limit of 40% opacity, meaning no more than 40% of the light can be obscured by its smoke. Newer engines have stricter limits (e.g., 5%–10% for 2007+ engines with DPF). We’ll let you know what standard applies to your vehicle and how your results compare.
In addition to the smoke meter test, we also conduct a Visual Emissions Control Equipment Inspection during this service. This means our technician will look at all the critical emissions components on your truck to ensure nothing is tampered with or malfunctioning. We check for the presence and condition of parts like the Diesel Particulate Filter (DPF), Exhaust Gas Recirculation (EGR) system, Selective Catalytic Reduction (SCR) system/DEF injection, and any other applicable equipment. The visual inspection is required by CARB as part of the Clean Truck Check for non-OBD vehicles. If we notice, for instance, a missing filter or an obvious tamper (like an EGR delete), we will inform you because that would need to be corrected to pass.
Our equipment: We use calibrated, CARB-approved smoke opacity meters that comply with SAE J1667. Our team is trained to administer the test properly, ensuring accurate results. The whole smoke test process typically only takes a few minutes, though we may advise you to avoid testing if certain conditions aren’t met (for example, excessive wind, or if the truck hasn’t sufficiently warmed up, as these can affect readings).
If your vehicle passes (opacity is under the limit and all required equipment is present and functional), we will record the passing result. Just like with OBD tests, we will submit the passing smoke test result to CARB’s database immediately. You’ll then be able to proceed with your registration or compliance verification. We can provide a copy of the Smoke Test Report for your records.
If your vehicle fails (opacity too high or a major equipment issue found), we’ll discuss what that means. High opacity could indicate problems like a clogged air filter, injector issues, or a malfunctioning DPF. We can guide you on potential remedies – for instance, performing needed engine maintenance or DPF cleaning and then scheduling a retest. We want to help you get into compliance. Minor issues (like a small exhaust leak that skewed the reading) can sometimes be fixed on the spot by our tech or your mechanic prior to retest.
Experienced diesel experts: We have years of experience working with diesel engines and emission control systems. We can often spot and help resolve issues that cause high smoke levels, saving you trial and error.
Mobile convenience: Older trucks, fleet vehicles, and even motorhomes or buses often need opacity tests – we come to wherever your vehicle is, whether it’s a fleet yard, farm, construction site, or garage. No need to drive a smoky vehicle miles to find a test station; we’ll be there.
Compliance confidence: By getting your opacity test done with us, you ensure all required steps are handled. We perform both the smoke test and visual inspection as mandated, so there are no surprises. We stay current on CARB regulations, so if standards or procedures update, you can be confident we’ll test accordingly.
Fast results: You will know immediately if your vehicle passed. We then take care of reporting it. Many customers appreciate that we can often do multiple trucks in one visit – for example, testing an entire fleet of older trucks efficiently, with fleet discounts available (call us to discuss if you have multiple vehicles).
A smoke opacity test is crucial for keeping your older diesel vehicles legal on California roads and doing your part for cleaner air. Our professional testing will give you a clear picture of your truck’s exhaust health. Schedule a smoke test with us and ensure your rig meets the mark. We’ll help you every step of the way so you can drive clean and stay compliant.
