FMCSR 393.83(b) Exhaust Discharge Citation: What Drivers Need to Know

Not necessarily. Across our 13 million inspection records, a 393.83(b) citation results in an out-of-service order only 17.4% of the time. That's significantly lower than the 31.4% average OOS rate across all FMCSR codes. Most drivers cited for exhaust discharging below the fuel tank or filler pipe—144 all-time citations in our database—are allowed to continue driving while they arrange repairs.

First: if your truck was placed out of service, contact your carrier or a repair facility immediately—you cannot legally operate until the exhaust system is corrected. Second: document the citation and inspection report with photos. Third: schedule repairs with a qualified technician who can verify the exhaust routing relative to the fuel tank location. Fourth: request reinspection once repairs are complete. If you were not placed OOS (the 82.6% majority case), arrange repairs within a reasonable timeframe to avoid escalation.

In the vehicle maintenance category, 393.83(b) is relatively uncommon—it ranks #1315 out of 3,036 FMCSR codes by enforcement volume. Inoperable lamps (393.9(a)) appear 4,588 times more frequently with a 15.4% OOS rate. Windshield defects (393.78) show a 0.3% OOS rate. The 17.4% OOS rate for 393.83(b) places it in the middle-to-upper severity range among equipment violations, indicating the violation is taken seriously when detected.

FMCSA assigns points to violations based on severity within their five-point safety BASICs. The exact point weight for 393.83(b) is not listed in our citation data, which means you should check your carrier's CSA Safety Management Cycle report or contact FMCSA directly for your specific score impact. What we can confirm: only 144 all-time citations exist in our database, so this is not a high-volume violation affecting broad driver populations.

Our inspection records do not break down 393.83(b) citations by state in a way that identifies concentrated regional enforcement patterns. With only 144 all-time citations and zero citations in the last 90 days across 13 million inspections, the violation is distributed too sparsely to point to specific high-citation states. If you received a citation, consult your inspection report for the enforcement location.

Moderately urgent. Our records show zero citations for 393.83(b) in the last 90 days and zero in the last 12 months, suggesting either repairs are happening quickly or inspectors are focusing enforcement on higher-frequency violations. However, if you were placed out of service (17.4% of cases), repair is mandatory before operation. If not OOS, arrange repairs within one to two weeks to reduce risk of a second citation or cascade into a safety audit.

Yes. FMCSA's DataQs program allows drivers and carriers to formally challenge inspection findings recorded in the Motor Carrier Management Information System (MCMIS). For a 393.83(b) citation—an equipment condition—you can contest if you believe the inspector incorrectly measured exhaust outlet position relative to the fuel tank, or if the violation was corrected before the report was finalized. Submit documentation (photos, repair receipts, technician statements) within 90 days of the inspection through the DataQs portal.

FMCSA CSA data is tracked by carrier USDOT number, not by individual driver. A 393.83(b) violation is recorded against the motor carrier's safety record and affects their CSA scores across the five BASICs. If you change carriers, the violation stays with your previous employer's record. However, your personal driving record within your carrier's system may reflect the citation. Ask your safety manager how your company logs driver citations internally.