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If you drive a diesel in Utah, you know the mountains aren't the only things with steep requirements. Between the infamous winter inversions and the "Diesel Brothers" lawsuit that made national headlines, Utah has become one of the strictest states in the West for diesel emissions enforcement.
At T3 Speed Shop, we get the same questions every day: "Do I need a test this year?" and "Why did my truck fail when it isn't throwing a code?" Here’s the breakdown of what you need to know to keep your rig on the road and out of the DMV’s crosshairs.
In Utah, your emissions requirements are determined by where you park your truck at night. If you live in Salt Lake, Davis, Utah, Weber, or Cache counties, you’re in the program.
For 2026, the testing schedule follows a specific model-year pattern:
Even-Numbered Model Years (e.g., 2020, 2022, 2024): You are due for a test in 2026.
Odd-Numbered Model Years (e.g., 2021, 2023, 2025): You’re generally good until 2027.
New Trucks: Most new diesel vehicles are exempt for the first five years, but don't let that make you lazy on maintenance.
At T3 Speed, we see it all—from guys who just want to keep their work trucks legal, to those who got "scammed" into illegal deletes and are now facing thousands in fines to put their trucks back to stock. Here is the straight talk on how to stay on the right side of the law in the Beehive State.
Emissions testing in Utah isn't statewide; it's a local game. Currently, only five counties require diesel emissions testing. If you’re registered in a rural county like Iron or Uintah, you’re in the clear for now—but if you’re on the Wasatch Front, the rules are tight.
|
County |
Testing Frequency |
Diesel Exemptions |
|
Salt Lake |
Biennial (years 2-6), then Annual |
1997 & older (under 14k GVWR) |
|
Davis |
Biennial (years 2-6), then Annual |
1997 & older |
|
Utah |
Annual (for 1998–2016) |
2017 & newer; 1997 & older |
|
Weber |
Biennial (years 2-6), then Annual |
1997 & older (under 14k GVWR) |
|
Cache |
Biennial (6 years and older) |
1997 & older; Under 6 years old |
https://dmv.utah.gov/register/inspections/
If you’re running a serious workhorse—anything over 14,000 lbs GVWR—the rules just changed. As of January 1, 2026, Utah has implemented a new "High Emissions Heavy Duty Vehicle" fee.
The Hit: If your truck is a 2009 model year or older, you’re looking at a $250 initial registration fee and a $45 annual compliance fee.
The Why: The state is putting pressure on older, "dirtier" fleets to modernize. These fees go directly into a fund meant to help update clean-air technology across the state.
We see guys all the time who think that because their Check Engine Light (CEL) is off, they’re golden. Not quite. In Utah, the test is a two-part punch:
The tech is going to look for "tampering." If you’ve got a "straight pipe" where your DPF (Diesel Particulate Filter) should be, or if your EGR (Exhaust Gas Recirculation) system has been "deleted," you fail instantly. No amount of "clean tuning" will save you from a missing piece of hardware.
For 2007 and newer diesels, the testing station plugs into your port to check your Readiness Monitors.
Mechanic's Tip: If you recently cleared a code or disconnected your battery to "trick" the system, your monitors will say "Not Ready." You’ll have to drive the truck for about 50–100 miles in various conditions to get those sensors to "set" before you can pass.
Don't wait until the week your tags expire to see if your truck is healthy. If you’ve noticed your fuel mileage dropping or your exhaust smelling "heavier" than usual, your emissions system might be soot-clogged.
We specialize in keeping these systems running at peak performance without sacrificing the reliability you need. Whether it’s a forced regen or fixing a sensor that’s about to give up the ghost, we’ll get you through the testing line without the headache.
Think your truck might fail due to a "Not Ready" monitor or a check engine light that won’t go away?
Your truck will not pass if it has a check engine light and readiness monitors. If you have 2 or more readiness monitors it will not pass emissions on newer then 2007.5 Diesel engines.
Check out our Diesel Truck Services at T3 Speed Shop and give us a call today!
Yes, but requirements depend on where the vehicle is registered. Currently, five counties—Salt Lake, Davis, Utah, Weber, and Cache—require diesel emissions testing, while most other counties do not. Testing frequency varies by county and vehicle age, often alternating between annual and biennial schedules.
Exemptions vary by county, but generally, diesel trucks from 1997 and older are exempt from testing in most participating areas. Additionally, new diesel vehicles are typically exempt for the first two to five model years depending on the specific county's regulations.
Yes, "deleting" a diesel truck is illegal under both Utah state law and federal law (the Clean Air Act). Tampering with or removing emissions control equipment like the DPF or EGR can result in failed inspections, heavy fines, and the suspension of your vehicle's registration.
