393.9BRKLAMP

393.9BRKLAMP Violation: Inoperative Brake Lamps

One or more brake lamps were recorded as inoperative when the service brakes were applied.

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Plain-English answer

What does violation code 393.9BRKLAMP mean?

One or more brake lamps were recorded as inoperative when the service brakes were applied.

Why carriers pay attention

How 393.9BRKLAMP can affect a trucking safety record

Brake-lamp findings may be out of service depending on how many required lamps fail and the applicable inspection criteria. The rearmost vehicle and lamp positions should be identified.

FMCSA inspection data can flow into the Safety Measurement System used to organize carrier performance into Behavior Analysis and Safety Improvement Categories, commonly called FMCSA SMS BASICs. The carrier should verify the inspection, the assigned BASIC, and whether the violation is included in the official calculation.

How it gets cited

Common 393.9BRKLAMP inspection situations

  • A stop lamp does not illuminate because of a bulb, connector, wiring, or power issue.

  • The tractor and trailer work separately, but a connection issue is attributed to the wrong unit.

DataQ review

When a 393.9BRKLAMP violation may deserve a closer look

A DataQ challenge should identify a specific factual or legal error in the inspection data. These are review questions—not assumptions that the violation should be removed.

Potential review angles

  • The lamp operated during inspection or the inspector tested the wrong circuit or unit.
  • The report identifies the wrong lamp position or rearmost vehicle.
  • The condition resulted from an inspection connection issue not present in normal operation.

Evidence to collect

  • Time-stamped video showing brake-lamp operation
  • Tractor and trailer electrical diagnostic results
  • Inspection report identifying the exact lamp and vehicle position
Compliance expert review

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DataQs changes in 2026

A stronger review process still requires a stronger record.

FMCSA’s 2026 DataQs overhaul adds independent review stages, decision deadlines, and more detailed explanations. Carriers still carry the burden of identifying the error and supporting the requested correction.

See the 2026 DataQs changes
Frequently asked questions

393.9BRKLAMP violation FAQ

What does a 393.9BRKLAMP violation mean?

One or more brake lamps were recorded as inoperative when the service brakes were applied.

Which FMCSA SMS BASIC is associated with 393.9BRKLAMP?

Code 393.9BRKLAMP is commonly associated with the Vehicle Maintenance BASIC in the FMCSA Safety Measurement System. Inclusion and weighting should be confirmed on the carrier’s official record.

Can a trucking company challenge a 393.9BRKLAMP violation?

A carrier may submit an FMCSA DataQs Request for Data Review when the underlying inspection data is incomplete or incorrect. A repair made after the inspection does not by itself prove the original 393.9BRKLAMP finding was wrong.

What evidence helps review a 393.9BRKLAMP violation?

Useful evidence may include time-stamped video showing brake-lamp operation, tractor and trailer electrical diagnostic results, inspection report identifying the exact lamp and vehicle position. The best evidence is tied to the cited vehicle, driver, location, and inspection time.

Keep reviewing

Related DOT violation codes

View all violation guides
393.9Inoperable Required LampLighting393.11Required Lamps and Reflective MaterialLighting396.17CNo Proof of Periodic InspectionInspection and maintenance393.75A3Flat Tire or Audible Air LeakTires and wheels

Source references: 49 CFR 393.9 and FMCSA roadside inspection data. This guide is general information and does not guarantee a DataQs outcome or replace legal advice.