Violation code

393.17B1-LDSML

Lighting - Driveaway, side marker lamp(s) missing on rearmost towed vehicle.

Vehicle Maintenance2Non-OOS· SMS Appendix A v3.20

393.17B1-LDSML is a Clearance Identification Lamps/Other violation under 49 CFR §393.17B1-LDSML. It falls in the Vehicle Maintenance BASIC with a severity weight of 2/10. Nationally it was cited 438 times in the last five years, with an OOS rate of 0.0%.

📊

National roadside inspection stats

as of 6/20/2026

Inspections

435

that found this code

Violations

438

total written

OOS rate

0.0%

0 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: Clearance Identification Lamps/Other
Regulation §: 393.17B1-LDSML
Severity weight: 2
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 393.17B1-LDSML in about 5 seconds. AI quotes the CFR, predicts your grant chance.

⚡ Draft a challenge →

Notes

DSMS: Y | Comment: Added in 3.15 to Lighting violation group; moved in 3.17 to Clearance Identification Lamps/Other violation group | 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; moved to Clearance Identification Lamps/Other violation group with February 23, 2024 snapshot.

📚

Challenging 393.17B1-LDSML through FMCSA DataQs

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

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 393.17B1-LDSML →Read the DataQs guide first

More codes in Vehicle Maintenance

Same BASIC category — ranked by national citation volume

View all Vehicle Maintenance codes →

Other Clearance Identification Lamps/Other codes

Codes under the same FMCSA violation group

❓

Frequently asked questions about 393.17B1-LDSML

What does violation 393.17B1-LDSML mean?

393.17B1-LDSML is the FMCSA roadside-inspection violation code for "Lighting - Driveaway, side marker lamp(s) missing on rearmost towed vehicle.", part of the Clearance Identification Lamps/Other group, cited under 49 CFR §393.17B1-LDSML.

What BASIC does 393.17B1-LDSML affect?

393.17B1-LDSML falls under the Vehicle Maintenance BASIC in the FMCSA Safety Measurement System (SMS).

What is the CSA severity weight of 393.17B1-LDSML?

393.17B1-LDSML carries a severity weight of 2 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 393.17B1-LDSML an out-of-service (OOS) violation?

No. 393.17B1-LDSML 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 393.17B1-LDSML add to a carrier's score?

The point contribution of 393.17B1-LDSML depends on its severity weight (2/10) 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 393.17B1-LDSML be challenged through DataQs?

Yes. If you believe 393.17B1-LDSML 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 393.17B1-LDSML Vehicle Maintenance BASIC Carrier CSA lookup CSA glossary

393.17B1-LDSML

National roadside inspection stats

Challenging 393.17B1-LDSML through FMCSA DataQs

Pre-trip inspection showed compliant brakes

Momentary failure exception (§393.9)

Tread measurement disputed

Documented maintenance schedule disproves the defect