What happens if you're cited for exhaust discharging below the fuel tank. OOS rates, state enforcement, and next steps based on 114 all-time citations.
Ranks #1,387 of 3,146 FMCSR codes by citation frequency • OOS rate of 19.8% is below the FMCSR-wide average of 33.3%.
Exhaust - Discharging below the fuel tank or filler pipe.
Direct answers grounded in TruckCodex inspection data
Not usually. Across our 13 million inspection records, 393.83B results in an out-of-service order only 20.2% of the time—well below the national average OOS rate of 31.4% for all FMCSR violations. Of 114 all-time citations in our database, 23 led to an OOS placement and 91 did not. However, the outcome depends on inspection circumstances and your state. In Texas, the most common citation state, the OOS rate climbs to 35.0%.
First, document the citation details and your vehicle's condition at the time of inspection. Second, inspect your exhaust system routing—specifically where it discharges relative to your fuel tank and filler pipe—and photograph the current position. Third, check for related defects: our data shows brake tubing/hoses inadequate (393.45B2UV), missing fire extinguishers (393.95A), and fuel system leaks (396.5B) often appear in the same inspections. Get a qualified mechanic to assess all three areas. Finally, contact your carrier's compliance team with photos and the repair timeline.
It's mid-range in severity. The 20.2% OOS rate for 393.83B sits below the 31.4% all-FMCSR average, making it less likely to ground your truck than typical violations. For context, fuel system leak citations (396.5B) appear together with 393.83B in 4 of our last 90-day inspections, and those carry broader enforcement patterns. However, 393.83B ranks #1380 out of 3,036 FMCSR codes by citation volume, so it's not heavily enforced nationwide. Most citations concentrate in Texas—20 in the last 180 days—suggesting regional inspection focus.
Texas dominates enforcement. Our records show 20 citations in Texas over the last 180 days, with a 35.0% out-of-service rate there. California follows distantly with 2 citations and 0% OOS rate. The remaining eight states in our top enforcement list—Indiana, Minnesota, Mississippi, New Hampshire, New Jersey, Nevada, New York, and Ohio—each had only 1 citation in that period. If you operate in Texas, exhaust system routing is clearly a priority in roadside inspections.
The regulation prohibits exhaust from discharging below the fuel tank or filler pipe. In practical terms, your exhaust outlet must be positioned higher than (or at minimum not directly below) your fuel tank and the opening where you fill it. If exhaust gases or hot exhaust residue can drip onto or near your fuel tank components, you're in violation. This applies regardless of whether fuel is actively leaking—it's about positioning and proximity. Inspectors look at the physical layout and routing of your exhaust system during roadside checks.
Citation volume is low but variable. Our 12-month trend shows a range from 2 citations (September 2025) to 10 citations (March 2026). Recent months averaged 6–9 citations per month. Over the last 90 days, we've recorded 20 citations total—roughly 7 per month. This is still far below high-volume codes like inoperable lamps (660,737 all-time citations), so 393.83B remains uncommon. The variability suggests regional inspection campaigns rather than consistent nationwide enforcement.
Yes, you can submit a DataQs (Roadside Examination Reporting System) challenge if you believe the citation is factually incorrect. DataQs disputes are filed through FMCSA within 90 days of the inspection. For a 393.83B citation, your challenge should focus on whether your exhaust outlet actually discharges below the fuel tank or filler pipe—provide photographs, vehicle specifications, or mechanic documentation showing the exhaust routing. If the inspector's measurement or positioning description was inaccurate, include that evidence. Document which part of your system was measured and how. DataQs disputes do not remove points immediately but create an official record if FMCSA overturns the violation.
Freightliners lead with 14 citations, followed by Kenworth at 12. Mack, Volvo, and 'other' makes each have 9 citations. Peterbilt and Freightliner-branded units account for 8 each. These numbers reflect both the prevalence of heavy-duty tractors in the fleet and differing design variations in exhaust routing across manufacturers. If you operate any of these models, pay extra attention to exhaust system positioning during pre-trip inspections and after any maintenance work involving exhaust components.
Where 393.83B is most commonly cited (last 180 days)
Other violations commonly found on the same inspection (last 90 days)
TruckCodex aggregates official public-sector datasets. See the Source registry for dataset-level coverage and the Freshness log for last-import timestamps.
Census, SAFER, SMS, Licensing & Insurance (L&I), roadside inspections, crashes, and authority history.
Vehicle recall campaigns, defect investigations, and consumer safety complaints (SCRS).
Cross-border carrier registry and Canadian recall campaigns where applicable.
TruckCodex is an independent aggregator; it is not affiliated with FMCSA, NHTSA, EIA, or Transport Canada. Always verify compliance-critical information directly with the originating agency.