What happens if you're cited for 393.83C improper exhaust on a gasoline-powered bus. Direct answers backed by 13M+ inspection records.
Ranks #2,295 of 3,146 FMCSR codes by citation frequency • OOS rate of 100.0% is above the FMCSR-wide average of 33.3%.
Improper exhaust - Bus (Powered by gasoline)
Direct answers grounded in TruckCodex inspection data
Yes. Across our inspection records, 393.83C citations result in an out-of-service placement 100% of the time—all 8 all-time citations in our database led to OOS. This is substantially higher than the national FMCSR average OOS rate of 31.4%, making this one of the most consistently enforceable violations. Your bus will be taken out of service at roadside until the exhaust defect is corrected.
Yes, significantly. While related codes like inoperable required lamps (393.9) have a 6.9% OOS rate and lighting defects (393.11) sit at 1.8%, the 393.83C improper exhaust violation carries a 100% OOS rate. Even strict maintenance codes like slack adjuster defects (393.47E) show 0% OOS placement. The data indicates improper exhaust is treated as an immediate safety-of-operation issue by inspectors.
It is very rare. Our database records only 8 all-time citations for improper exhaust on gasoline-powered buses, with just 3 citations in the last 12 months and 1 in the last 90 days. This ranks 393.83C at #2269 out of 3,036 FMCSR codes by citation volume. For context, inoperable required lamps (393.9) has 180,097 citations—so improper exhaust on bus is cited roughly 22,500 times less frequently.
In the last 180 days, Iowa and Illinois each recorded 1 citation for 393.83C, both resulting in out-of-service placements. These are the only two states with recorded citations in that period. The low overall volume means geographic patterns are limited, but data shows enforcement when it does occur is consistent and results in immediate OOS action.
Potentially, yes. DataQs allows drivers and carriers to challenge roadside inspection records through the FMCSA's formal record dispute process. However, improper exhaust is an observable equipment defect—not a documentation or paperwork issue—so success depends on whether the citation was factually incorrect (e.g., inspector misidentified the exhaust system component). If your exhaust system was actually compliant, file a DataQs challenge with photo evidence. If defective, focus energy on repair and compliance rather than dispute.
Extremely urgent. You cannot legally operate the bus until the exhaust is repaired—the citation places you out of service immediately. The data shows 100% of 393.83C violations result in OOS status with no exceptions in our 13 million inspection records. Additionally, the violation involves a gasoline-powered bus engine exhaust system, which is a direct safety and emissions concern. Repair should happen within 24–48 hours to minimize operational downtime.
Rural Transit Enterprises Coordinated Inc (USDOT 691393) has the highest citation count with 2 citations for 393.83C all-time. Five other carriers—Sharp Healthcare, First Student Inc, C 9 Transportation Inc, Echo Windy City LLC, and Bus Party Okoboji LLC—each have 1 citation on record. Small sample size reflects the rarity of this violation across the industry. Ford vehicles account for 7 of 8 all-time citations.
Where 393.83C is most commonly cited (last 180 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.
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