What 393.9B-LPL means in plain language
A 393.9B-LPL citation means an inspector found one or more of your parking lamps blocked, covered, or otherwise obscured and not functioning as designed. Parking lamps are the smaller lights mounted on the front and rear corners of your vehicle—they're separate from your main headlights, taillights, and turn signals.
Obscuration can happen in several ways: dirt or road grime buildup, damage that cracked a lens, a dent that pushed the lamp inward, or something physically covering the lamp (like a misaligned bumper, broken trim, or debris). The regulation requires these lamps to be visible and operational so other drivers can see your vehicle in low-light conditions.
This is a vehicle maintenance citation, not a driver behavior violation. The fix is straightforward: clean or replace the obscured lamp(s) and verify they illuminate when powered on.
What our enforcement data actually shows
Across our 13 million+ inspection records, 393.9B-LPL is a low-frequency, low-severity citation. We have recorded 37 all-time citations for this code, with 19 citations in the last 12 months and 4 in the last 90 days. None of these 37 citations—zero—resulted in an out-of-service order, giving this code a 0.0% OOS rate.
For context, the all-FMCSR average OOS rate is 31.4%. This code ranks #1717 out of 3,036 FMCSR codes by citation volume, placing it well outside the most commonly enforced violations. The monthly trend over the past 12 months shows sporadic activity: 2 citations in May 2025, a spike to 4 in September 2025, and then 1 to 3 citations per month through early 2026. This pattern suggests it is not systematically targeted but rather cited opportunistically during routine inspections when an inspector spots the defect.
The fact that zero citations have triggered out-of-service status tells you that inspectors and enforcement jurisdictions do not regard obscured parking lamps as an immediate safety threat requiring you to stop operations. You can usually correct this defect and continue your trip or your operating day.
Who gets cited most
Our data from the last 180 days shows Pennsylvania leads with 3 citations, followed by Nevada with 2 citations. Connecticut, Kansas, New Jersey, Alabama, South Carolina, and Arizona each recorded 1 citation. All eight states maintained a 0.0% OOS rate for this code, meaning no driver cited in any of these jurisdictions was pulled out of service.
Among carriers, our all-time records show Quality Tank SA de CV (USDOT 2864600) with 4 citations—the highest count in the dataset. The remaining carriers cited for this violation each appear once or twice. These numbers reflect the relative rarity of this citation; no single carrier stands out as having systemic parking-lamp problems across a fleet.
How severe is this compared to similar codes
Parsing the vehicle maintenance category, this code sits at the lower end of enforcement and severity. For comparison: 393.9(a)—Inoperable required lamps—has generated 660,737 citations with a 15.4% OOS rate, making it far more frequent and slightly more likely to result in out-of-service status. The code 396.3(a)(1)—Inspection/repair/maintenance general—has 236,919 citations and a 45.3% OOS rate, indicating much broader maintenance concerns and much stricter enforcement.
Another peer code, 393.11 (Lighting devices/reflectors), shows 179,734 citations with only a 1.8% OOS rate, similar in severity to 393.9B-LPL. The code 393.78 (Windshield condition defective) has 157,894 citations and a 0.3% OOS rate, slightly lower OOS risk. These comparisons show that minor lighting defects—when they do not render lights completely inoperable—are treated as maintenance write-ups rather than roadside stopping violations.
How to avoid it
Preventing a 393.9B-LPL citation requires attention during your pre-trip and en-route inspections:
-
Walk around and inspect all lighting surfaces. Before each trip, physically walk the perimeter of your vehicle. Look at the front and rear parking lamps (usually small, amber or white lights on the corners). Wipe away any accumulated dirt, road salt, or grime with a cloth. If a lens is cracked, fogged, or severely dulled, note it and report it to maintenance.
-
Check lamp functionality. Turn on your parking lights (sometimes labeled "position lights" or "running lights") while parked and have a spotter or colleague confirm that both front and rear parking lamps illuminate. If one does not light, document the defect immediately and schedule repair.
-
Inspect for physical damage and trim misalignment. Look for bumper dents, trim pieces, or body damage that might push a lamp inward or cover it. After an accident or rough handling, pay extra attention to the lamp housings.
-
Report recurring issues early. Our co-occurring data shows that when 393.9B-LPL appears alongside other citations, issues like turn-signal obscuration (393.9B-LTSO) and lack of proof of periodic inspection (396.17C-PI) are common. If you notice your lights are dirty or damaged, get a full lighting system check from your carrier's maintenance team before you hit the road. Do not defer lighting maintenance.
-
Vehicle-specific awareness. Our records show Freightliner units account for the highest count of citations for this code. If you operate a Freightliner, be especially vigilant about front and rear corner lamp cleanliness and condition, as these vehicles may have lamp housings more prone to dirt accumulation or damage in certain configurations.
Your citation is a maintenance notice, not a failure of your driving or safety practices. A quick lamp cleaning or replacement, documented and noted in your vehicle's maintenance log, will resolve the issue and lower your risk of future stops for this violation.