FMCSR 393.80A – Defective Exhaust System: Driver Q&A

Almost certainly not. Across all-time inspection records, 393.80A carries a 0.4% out-of-service rate — only 14 trucks placed OOS out of 3,335 total citations. For context, the all-FMCSR average OOS rate sits at 31.4%, so this code runs roughly 78 times below that average. You will almost always be allowed to keep driving after receiving this citation, but the violation still lands on your inspection report and feeds into CSA scoring, so it should not be ignored.

A 393.80A citation carries a CSA severity weight of 4. That base number is then multiplied depending on how recently the inspection occurred: violations within 6 months receive a 3× time-weight multiplier, violations between 6 and 12 months get 2×, and violations older than 12 months carry 1×. So a fresh 393.80A citation effectively counts as 12 severity points in the Vehicle Maintenance BASIC until it ages past six months. Accumulating points in that BASIC can trigger FMCSA interventions for your carrier.

Take these steps immediately:

1. Document the exhaust system — photograph the leak point, loose mounting, or discharge location before any repair.
2. Schedule repair promptly — a certified mechanic should address the defect and provide a signed repair order.
3. Check the whole truck. Our inspection records show that in the last 90 days, 393.80A citations appeared in the same inspection as glazing/window obstructions (393.60C, 96 shared inspections), hood-securing defects (393.203C-CBP, 77 shared inspections), and fuel system leaks (396.5B-L, 65 shared inspections). Inspectors who find one maintenance issue tend to find others — fix everything before your next stop.
4. Keep the repair receipt in the cab for at least 90 days.

It is moderate in severity. The 0.4% OOS rate on 393.80A is well below most peers in the Vehicle Maintenance category. For comparison, our inspection records show that 396.3(a)(1) — general inspection/repair/maintenance — carries a 45.3% OOS rate across 236,919 citations, and 393.9(a) for inoperable required lamps runs a 15.4% OOS rate across 660,737 citations. With 3,335 all-time citations, 393.80A ranks #414 out of 3,036 FMCSR codes by volume — present often enough to matter, but far less likely to ground your truck than many other maintenance violations.

Yes, you can challenge it. FMCSA's DataQs system (the Request for Data Review, or RDR process) lets drivers and carriers submit a formal dispute against any inspection finding. Because 393.80A is an equipment violation — not a documentation issue — a successful challenge typically requires evidence that the cited defect did not actually exist at the time of inspection. Useful evidence includes dated repair records showing the exhaust system was in compliance before the stop, photos taken at the scene, or a mechanic's signed inspection report. Submit through the DataQs portal at dataqs.fmcsa.dot.gov and track the RDR case number provided.

Georgia leads by a wide margin. Our inspection records for the last 180 days show Georgia issued 117 citations for 393.80A — more than double the next states on the list. Washington came in second with 60 citations, followed closely by federal inspections (US jurisdiction) at 59, New Jersey at 58, and New York at 56. If your lanes run through the Southeast or the Northeast corridor, enforcement exposure for this code is noticeably higher. New Jersey is also the only top state where any trucks were placed out of service — 1 OOS out of 58 citations, a 1.7% rate.

Do not wait. While the 0.4% OOS rate means the defect rarely stops a truck at inspection, our records show 393.80A is being written at an accelerating pace: 1,755 citations in the last 12 months, with 330 of those in just the last 90 days. Monthly counts peaked at 181 in 2025-07. An unrepaired exhaust defect also creates real safety risk — leaking exhaust gases can enter the cab — and the CSA severity weight of 4 starts aging down only after you fix it and stay clean. A leaking or unsecured exhaust system that gets caught on consecutive inspections compounds your BASIC score fast.

Both are affected, but in different ways. The Vehicle Maintenance BASIC score where 393.80A lands is attributed primarily to the carrier, since the carrier is responsible for ensuring the vehicle is roadworthy before dispatch. However, if the driver conducted or signed off on a pre-trip inspection and the defect was present and detectable, the driver's own inspection record can also reflect the finding. Our records show carriers like FEDERAL EXPRESS CORPORATION (27 all-time citations) and J B HUNT TRANSPORT INC (16 citations) have accumulated 393.80A hits across their fleets — fleet-wide patterns in BASIC scoring are what typically trigger FMCSA interventions.