393.9 Violation: What It Means and How to Fix It
Data through September 24, 2026 · Last updated October 28, 2026 · By Chad Griffith, founder
Quick Answer
393.9 (Lamps operable, prohibition of obstructions of lamps and reflectors) was cited 182,586 times in roadside inspections of interstate for-hire carriers with 5 to 50 trucks from September 25, 2024 to September 24, 2026, and 16.8% of those citations put the driver or vehicle out of service. The most common version is 393.9: Inoperable Required Lamp.
182,586
Citations on carriers with 5 to 50 trucks
16.8%
Out of service
1,023,626
All carriers, same period
What the rule says
Every lamp the regulations require must work at all times (49 CFR 393.9(a)). The sub-code on the report names the lamp: identification, clearance, turn signal, stop, head, tail or license plate.
When it puts you out of service
A single lamp out is rarely out of service. Both stop lamps out, or a rear turn signal out on the rearmost vehicle, usually is (393.9A-LSLIWR and 393.9A-LTSI are 99% and 98% out of service in this data).
The codes on the inspection report
| Code | What the officer wrote | Severity weight | Citations, 5 to 50 trucks | Out of service |
|---|---|---|---|---|
| 393.9 | “Inoperable Required Lamp” | 2 | 23,537 | 10.5% |
| 393.9A-LIL | “Lighting - Identification lamp(s) inoperative” | 2 | 17,635 | 0.0% |
| 393.9A-LFTSI | “Lighting - Front - Turn signal - inoperative” | 6 | 14,172 | 0.1% |
| 393.9A-LCL | “Lighting - Clearance lamp(s) inoperative” | 2 | 10,949 | 0.0% |
| 393.9A-LTSI | “Lighting - Turn signal - Any inoperative on the rearmost vehicle.” | 6 | 10,926 | 97.7% |
| 393.9A-LHLI | “Lighting - Headlamp(s) - Any inoperative” | 6 | 10,477 | 0.0% |
| 393.9A-LSLIWR | “Lighting - Stop lamps - Both inoperative when required to be on” | 6 | 10,383 | 99.3% |
| 393.9A-LSLI | “Lighting - Stop lamps - Any inoperative.” | 6 | 10,308 | 4.3% |
| 393.9A-LLPL | “Lighting - License plate lamp inoperative” | 2 | 9,995 | 0.0% |
| 393.9TS | “Inoperative turn signal” | 6 | 9,977 | 35.3% |
| 393.9A-LRLI | “Lighting - Tail lamp - Any inoperative” | 6 | 8,880 | 0.9% |
| 393.9A-LSML | “Lighting - Side marker lamp(s) inoperative” | 2 | 8,852 | 0.0% |
How it scores (violation points)
How it scores: in FMCSA's Safety Measurement System each violation counts its severity weight, plus 2 if it put the driver or vehicle out of service, times 3 in its first 6 months, 2 from 6 to 12 months, and 1 from 12 to 24 months. FMCSA has approved a simpler scale that is not live yet.
How to fix it
- Replace the bulb, lamp or wiring before the unit runs again, and keep the repair receipt or work order.
- Have the repair certified on the driver vehicle inspection report if one was written (49 CFR 396.11(a)(3)).
- Check every other lamp on that unit and its trailer the same day.
Stop it happening again
- Make a walk-around lamp check part of every pre-trip inspection (49 CFR 396.13).
- Swap failed incandescent lamps for sealed LED units at the next service.
Challenging it in DataQs
Use DataQs (dataqs.fmcsa.dot.gov) only when the report is wrong: the wrong carrier or vehicle, a violation that did not happen, or a citation a court dismissed without a fine or found you not guilty of, which removes it from the Safety Measurement System; a conviction of a different charge lowers its weight to 1 (FMCSA adjudicated citations policy). Fixing the defect afterward is not a reason to remove it; keep the repair record instead.
FileFlo reads your public FMCSA record, lists every violation with the rule behind it, and keeps the driver and vehicle records that stop repeats.
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About these numbers
Counts are violations cited in roadside inspections used in FMCSA's Safety Measurement System from September 25, 2024 to September 24, 2026 (dataset 8mt8-2mdr on data.transportation.gov, October 2026 run). Carriers with 5 to 50 trucks means 66,936 active interstate for-hire carriers with 5 to 50 power units and more trucks than buses, based in the 50 states or DC, from FMCSA's census file. This is FileFlo's reading of public FMCSA data, not an FMCSA rating. Severity weights are the current SMS weights.