Violation code

393.9B-LHLO

Lighting - Headlamp(s) - Any obscured.

Vehicle Maintenance6Non-OOS· SMS Appendix A v3.20

393.9B-LHLO is a Lighting violation under 49 CFR §393.9B-LHLO. It falls in the Vehicle Maintenance BASIC with a severity weight of 6/10. Nationally it was cited 425 times in the last five years, with an OOS rate of 0.2%.

📊

National roadside inspection stats

as of 6/20/2026

Inspections

424

that found this code

Violations

425

total written

OOS rate

0.2%

1 OOS

Source: FMCSA roadside inspection data (last 5 years). The OOS rate is the share of these violations that led the officer to mark the driver or vehicle out of service.

Violation group: Lighting
Regulation §: 393.9B-LHLO
Severity weight: 6
Used in SMS: Yes
Status: Active
Updated: 6/20/2026

Last updated June 2026

⚡

Think this violation was written incorrectly?

Generate a polished DataQs challenge letter for 393.9B-LHLO in about 5 seconds. AI quotes the CFR, predicts your grant chance.

⚡ Draft a challenge →

Notes

DSMS: Y | Comment: Added in 3.15 | Footnote: As of February 1, 2023, the violations in this table are included in SMS. Only violations cited on or after February 1 are included in SMS calculations. This update aligns SMS with how violations are being cited in a new software used for roadside inspections.

📚

Challenging 393.9B-LHLO through FMCSA DataQs

If this violation was written incorrectly, here are the angles trucking-safety managers use to contest it. Playbook: Vehicle Maintenance (general).

Relevant 49 CFR49 CFR § 393.9

Lamps operable, prohibition of obstructions

“All lamps required by this subpart shall be capable of being operated at all times. This section shall not be construed to prohibit motor vehicles being operated with lamps that are momentarily inoperative due to vibration, temperature, or similar transient causes.”

Common ways to challenge this code

Pre-trip inspection showed compliant brakes
The driver's pre-trip DVIR documented compliant brake adjustment and operation. The cited defect arose en route or was misclassified at roadside.
Evidence that wins
- ✓Driver Vehicle Inspection Report (DVIR) from that date
- ✓Repair invoice or shop record
- ✓Post-citation re-inspection certificate (clean)
Momentary failure exception (§393.9)
The required lamp was inoperative only momentarily due to vibration, temperature, or similar transient cause — explicitly exempted under §393.9.
Evidence that wins
- ✓Photograph showing the lamp operable before / after the stop
- ✓Repair invoice if a fuse or bulb was replaced
Tread measurement disputed
The tread depth measurement was taken at a worn point that is not representative, contrary to NHTSA/FMCSA measurement standards.
Evidence that wins
- ✓Independent tread gauge reading from same tire (multiple positions)
- ✓Photograph of the tire with a reference scale
Documented maintenance schedule disproves the defect
Carrier's periodic-inspection records show the cited defect could not reasonably have existed at the time of inspection.
Evidence that wins
- ✓Periodic inspection certificate (§396.17)
- ✓Maintenance work order proximate to inspection date

Common pitfalls — avoid these

⚠DataQs cannot remove a violation simply because the defect was repaired after the stop

⚡ Draft a challenge for 393.9B-LHLO →Read the DataQs guide first

More codes in Vehicle Maintenance

Same BASIC category — ranked by national citation volume

View all Vehicle Maintenance codes →

Other Lighting codes

Codes under the same FMCSA violation group

❓

Frequently asked questions about 393.9B-LHLO

What does violation 393.9B-LHLO mean?

393.9B-LHLO is the FMCSA roadside-inspection violation code for "Lighting - Headlamp(s) - Any obscured.", part of the Lighting group, cited under 49 CFR §393.9B-LHLO.

What BASIC does 393.9B-LHLO affect?

393.9B-LHLO falls under the Vehicle Maintenance BASIC in the FMCSA Safety Measurement System (SMS).

What is the CSA severity weight of 393.9B-LHLO?

393.9B-LHLO carries a severity weight of 6 out of 10. Higher weights indicate violations more closely tied to crash risk, and they count more toward a carrier's Vehicle Maintenance score.

Is 393.9B-LHLO an out-of-service (OOS) violation?

No. 393.9B-LHLO is not an out-of-service violation, so on its own it does not trigger an out-of-service order at the roadside.

How many CSA points does 393.9B-LHLO add to a carrier's score?

The point contribution of 393.9B-LHLO depends on its severity weight (6/10) multiplied by a time weight of 3, 2, or 1 based on how recent the inspection is. You can calculate the exact contribution with the CSA points calculator.

Can 393.9B-LHLO be challenged through DataQs?

Yes. If you believe 393.9B-LHLO was recorded in error, you can file a Request for Data Review (RDR) through the FMCSA DataQs system with supporting evidence. A successful challenge can remove or correct the violation on your record.

Keep going

CSA points calculator How to challenge a violation Draft a DataQs letter for 393.9B-LHLO Vehicle Maintenance BASIC Carrier CSA lookup CSA glossary

393.9B-LHLO

National roadside inspection stats

Challenging 393.9B-LHLO through FMCSA DataQs

Pre-trip inspection showed compliant brakes

Momentary failure exception (§393.9)

Tread measurement disputed

Documented maintenance schedule disproves the defect