393.83(a) Exhaust System Location Defects: Citations & OOS

Yes—but only about half the time. Across our inspection records, 393.83(a) citations result in an out-of-service order 51.1% of the time. This is notably higher than the national average OOS rate of 31.4% across all FMCSR codes. Whether your truck gets placed OOS depends on the specific hazard: if the exhaust system is actively burning or charring wiring or fuel lines, an inspector will typically order immediate repair before you operate. If the defect is minor or the hazard is not yet acute, you may receive a citation to repair within a compliance window.

This violation carries a CSA severity weight of 5 points. The actual number of points added to your driver history depends on when the citation was issued within the 30-day rolling window and how many other violations you've accumulated in the same category. CSA points decay over 36 months, so the impact diminishes over time if you have no further violations. Contact your carrier or FMCSA's Safety Management System to see your current CSA score.

Immediate steps:

1. Do not operate if the citation resulted in an OOS order—wait for repair and re-inspection.
2. Document the repair: Photograph the exhaust system before and after corrective work. Keep all service records.
3. Schedule inspection: Contact your carrier's maintenance team or a certified repair shop immediately.
4. Verify routing: Ensure the exhaust system is re-routed away from fuel lines, electrical harnesses, and combustible materials.
5. Request re-inspection: Once repaired, have an authorized inspector verify compliance before returning to service.

Delays in repair increase the risk of a second citation and higher CSA impact.

393.83(a) is moderately serious. Its 51.1% out-of-service rate exceeds the all-FMCSR average of 31.4%, putting it above most vehicle maintenance violations. For comparison, inoperable required lamps (393.9(a)) has a 15.4% OOS rate, while general inspection/repair violations (396.3(a)(1)) run 45.3%. The high OOS rate on 393.83(a) reflects the fire hazard: exhaust systems can ignite fuel or electrical components, creating acute safety risk that inspectors treat seriously.

Yes. If you believe the citation is factually incorrect or that you corrected the defect before the inspection, you can request a DataQ (Data Quality challenge) through FMCSA's Safety Management System. DataQs focus on accuracy and timeliness—not on whether the citation itself was justified. You'll need supporting documentation: photos, service records, or proof of repair date. Submit your DataQ within the allowed window to have your carrier's record corrected if the challenge is successful.

393.83(a) is relatively uncommon. Across our database of 13+ million inspection records, this code ranks #910 out of 3,036 FMCSR codes by all-time citation volume, with only 511 citations ever recorded. In the past 12 months, we have seen zero citations for this violation, which suggests improved exhaust system design and maintenance practices in the industry. However, when it does occur, the high OOS rate means the defect is treated as urgent.

Very urgent. With a 51.1% OOS rate, there is a significant chance your vehicle will be removed from service until repaired. Even without an OOS order, operating with a defective exhaust system risks additional citations and potential safety incidents. The defect—exhaust routing that can burn or char wiring, fuel lines, or combustible materials—creates a genuine fire or electrical failure hazard. Schedule repair within 24 hours of citation if not already out of service.

Freightliner tractors dominate the citation data: FREIGHTLIN (18 citations) and FRHT (21 citations) together account for about 76 of the 511 all-time citations. Other commonly cited makes include Peterbilt (PTRB, 18 citations), Ford (15 citations), Kenworth (KW, 14 citations), and Volvo (14 citations). This distribution reflects the prevalence of these makes in commercial fleets, not necessarily higher defect rates. Work with your maintenance team to verify exhaust routing on your specific model.