What 393.83F means in plain language
Your exhaust system has been temporarily repaired using wraps or patches instead of proper replacement parts. This violation occurs when an inspector finds evidence that your exhaust has been patched, taped, wrapped, or otherwise held together with temporary fixes rather than genuine replacement components or factory welds.
The exhaust system's primary job is to safely direct hot gases and emissions away from your truck and any occupants. When you use temporary repairs—whether it's exhaust tape, wrap, hose clamps, or patches—you're creating a solution that won't hold up under the heat, vibration, and pressure of highway driving. These quick fixes typically fail quickly, creating leaks that can harm your vehicle's performance and your safety record.
Federal regulations require that exhaust components meet their original specifications. A wrapped or patched exhaust is considered substandard because it doesn't meet those specifications and creates ongoing risk. The expectation is that you replace the damaged section with proper parts, not temporarily seal it.
What our enforcement data actually shows
Across our 13 million inspection records, 393.83F is cited at a relatively low volume compared to the broader FMCSR catalog. We've recorded 728 all-time citations, with 480 in the last 12 months and 145 in the last 90 days. This ranks the code at #805 out of 3,036 FMCSR codes by citation frequency.
The critical piece for drivers is the out-of-service rate: only 0.3% of 393.83F citations result in an out-of-service order. That means 2 trucks out of 726 total citations were pulled from service. For context, the all-FMCSR average out-of-service rate is 31.4%, so 393.83F is far less likely to result in an immediate roadside out-of-service order than the typical violation.
However, "not out-of-service" does not mean "no consequence." The citation remains on your vehicle inspection report, contributes to your carrier's safety rating, and can lead to follow-up inspections or enforcement attention if the problem isn't corrected quickly.
Looking at the 12-month trend, citations have been fairly consistent, ranging from 11 to 73 per month. February 2026 saw the highest volume at 73 citations, suggesting that winter months may correlate with more exhaust damage and temporary repairs—likely due to road salt, thermal stress, and delayed maintenance decisions.
Who gets cited most
Our inspection records show Texas dominates 393.83F enforcement, accounting for 203 citations over the last 180 days with 1 out-of-service order (0.5% OOS rate). That's by far the largest share of national citations. The next entries are significantly smaller: US (federal inspection sites) recorded 37 citations with 0 OOS events (0.0% rate), California had 5 citations with 0 OOS events (0.0% rate), and New Mexico also reported 5 citations with no out-of-service outcomes.
The variation in OOS rates across these states is minimal, so geography doesn't meaningfully shift the likelihood of immediate removal from service. Texas's slightly higher rate (0.5% vs. 0.0% in other states) reflects the larger sample size rather than a fundamentally different enforcement approach.
Top carriers cited include fleets such as Sama Freight S De Rl De CV (8 citations) and Grupo Iglesias Hidrocarburos SA De CV (7 citations) over the full dataset. These numbers reflect exposure rather than an indicator of fleet-wide neglect—larger fleets operating more miles naturally accumulate more citations. The pattern suggests that 393.83F is widely distributed across carrier types and sizes.
How severe is this compared to similar codes
Within the vehicle maintenance category, 393.83F sits at the lower end of enforcement severity. Compare it to peer violations:
393.9 (Inoperable Required Lamp) has generated 180,097 citations with a 6.9% out-of-service rate—roughly 23 times more citations and a significantly higher OOS rate than 393.83F.
393.78 (Windshield Condition Defective) shows 157,894 citations and a 0.3% OOS rate—nearly 217 times the citation volume, though identical OOS rate. This suggests windshield citations are far more frequent but similarly unlikely to trigger immediate removal.
396.3(a)(1) (Inspection/Repair/Maintenance—General) has 236,919 citations and a 45.3% OOS rate. This broad maintenance category catches vastly more violations and is far more likely to put you out of service.
The contrast is clear: 393.83F is a comparatively narrow, lower-frequency citation with minimal out-of-service risk, but it's not insignificant—it still represents a safety and compliance gap that needs fixing.
How to avoid it
Based on patterns in our 13 million inspection records, drivers cited for 393.83F often have co-occurring violations in related systems. Here's how to stay ahead of it:
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Inspect your entire exhaust from front to back during pre-trip. Look for discoloration, cracks, loose or hanging sections, or any visible wrapping, tape, or clamps. Don't assume a wrap is "fine for now"—inspectors will cite it immediately.
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Check fuel system integrity alongside exhaust. Our data shows fuel system leaks (396.5B) appear together with exhaust citations in 50 shared inspections over 90 days. A leaking fuel line can damage nearby exhaust components; fix fuel leaks promptly to prevent secondary exhaust damage.
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Monitor brake tubing and hoses. Brake tubing and hose damage (393.45B2UV) co-occurs in 41 shared inspections. Vibration and heat that degrades brake lines also stresses exhaust systems. A thorough underbody walk-around catches both.
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Pay special attention if you drive a Freightliner, Kenworth, or Utility vehicle. Our records show Freightliner (169 citations), Kenworth (135 citations), and Utility (62 citations) models are cited most often for 393.83F. These popular trucks may have more miles and age in the fleet, making preventive exhaust maintenance even more critical.
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If you spot exhaust damage, replace the section—don't wrap it. A $300–$600 exhaust replacement is cheaper and faster than a citation, a repair order, and follow-up inspection. Wraps are temporary theater; inspectors see through them every time.
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Schedule exhaust inspection during routine maintenance. Don't wait for a roadside citation to discover the problem. A quick visual check at every oil change or fuel stop can catch cracks before they become citations.
The bottom line: this violation is easy to avoid with basic pre-trip discipline. Check for wraps and patches, replace damaged sections properly, and keep your exhaust system in factory spec. You'll stay compliant and off the hook for a citation.