393.9B-LSLO: Obscured Stop Lamps — Will My Truck Get Put Out of Service?

No—this violation will almost certainly not ground your truck. Across our inspection records, only 2.5% of 393.9B-LSLO citations result in an out-of-service order. That's 16 OOS placements out of 638 all-time citations. Compare that to the national average OOS rate of 31.4% across all FMCSR codes: obscured stop lamps are treated as a lower-severity vehicle defect. You can typically drive to a repair facility, but do not delay the fix.

First, verify your stop lamps are actually obscured (mud, debris, damage) and document the condition with photos before repair. Second, inspect your turn signals and tail lamps—our data shows that 393.9B-LTSO (obscured turn signals) and 393.9B-LRLO (obstructed tail lamps) co-occur in the same inspections 23 and 16 times respectively in the last 90 days, meaning inspectors often find multiple lighting defects at once. Third, check your vehicle's periodic inspection records; 396.17C-PI (no proof of inspection) appears together with this code 18 times. Finally, schedule a certified repair and request written proof of correction for your safety file.

It is low-to-moderate severity. The 2.5% OOS rate makes it one of the least-critical citations in the vehicle maintenance category—far below the 31.4% national average. For context, 393.9(a) Inoperable Required Lamps carries a 15.4% OOS rate, and 396.3(a)(1) Inspection/Repair/Maintenance has a 45.3% rate. Obscured stop lamps rank #848 of 3,036 FMCSR codes by citation volume, meaning they're cited far less frequently than systemic maintenance failures. Fix it promptly but don't panic—this is not a critical out-of-service defect.

In the last 180 days, California leads with 20 citations (15.0% OOS rate), followed by Pennsylvania with 19 citations (5.3% OOS rate) and Florida with 11 citations (0.0% OOS rate). If you operate in California, note that inspectors there placed 3 of 20 violators out of service—higher than the national 2.5% rate for this code. Kansas and Arizona each had 10 citations with zero OOS placements. If you're in a high-citation state like CA or PA, stay ahead with regular pre-trip lighting checks.

Very urgent—repair within 24–48 hours. In the last 90 days, 89 citations were issued, and the monthly trend shows sustained enforcement: January 2026 had 46 citations, February 36, and March 32. Stop lamps are safety-critical; even though OOS rates are low, a blind stop lamp increases rear-end collision risk and invites follow-up inspections. Additionally, co-occurring codes like 392.2 (operating while ill or fatigued, 24 shared inspections) suggest that inspectors citing obscured lamps are also scrutinizing driver fitness and maintenance patterns. Schedule the repair immediately.

You can challenge the citation through the FMCSA's DataQs portal if you believe the inspector made a factual error—for example, if the lamp was not actually obscured, was obscured only by temporary debris, or if the inspector failed to follow proper inspection procedure. DataQs is most effective for documentation and procedural disputes. However, if an inspector photographed or clearly observed an obscured stop lamp during the roadside inspection, the violation is straightforward to defend. Focus your challenge on procedure: was the truck properly positioned for inspection, was the lamp actually obscured vs. simply dirty, etc.

This violation attaches to both. The roadside inspection report is filed under your carrier's USDOT number and affects your company's FMCSA safety record and Compliance, Safety, Accountability (CSA) scores. However, if your carrier can demonstrate you received proper vehicle pre-trip training and the defect was not visible during your pre-trip inspection (e.g., lamp got obscured during the trip), the carrier may dispute the finding or use it as a coaching opportunity rather than a mark against your driving record. Either way, the citation is on your inspection history and your carrier's data—both matter for hire-ability and rate quotes.

Because a single roadside inspection often uncovers multiple defects. In the last 90 days, obscured stop lamps appeared alongside obscured turn signals (393.9B-LTSO) 23 times, and with tail lamp obstructions (393.9B-LRLO) 16 times. This pattern tells you that if one lamp is blocked—by dirt, damage, or poor installation—others likely are too. It also suggests inspectors are doing thorough multi-lamp checks. When you fix the stop lamp, run a full lighting diagnostic: headlamps, turn signals, tail lamps, and clearance lights. The cost of a complete lighting inspection now will prevent repeat citations and keeps your CSA record cleaner.