Violation code

393.70B1II

Defective / Improper fifth wheel assembly upper half

Vehicle Maintenance3Non-OOS· SMS Appendix A v3.20

393.70B1II is a Coupling Devices violation under 49 CFR §393.70B1II. It falls in the Vehicle Maintenance BASIC with a severity weight of 3/10. Nationally it was cited 583 times in the last five years, with an OOS rate of 41.3%.

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National roadside inspection stats

as of 9/20/2026

Inspections

553

that found this code

Violations

583

total written

OOS rate

41.3%

241 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: Coupling Devices
Regulation §: 393.70B1II
Severity weight: 3
Used in SMS: Yes
Status: Active
Updated: 9/20/2026

Last updated September 2026

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Notes

DSMS: Y

What 393.70B1II means — and how to avoid it

In plain English

In plain terms, 393.70B1II is cited for defective / Improper fifth wheel assembly upper half. It falls under the FMCSA rules on parts and accessories needed for safe operation.

What the inspector checks

•Cracked/broken wheels or rims
•Loose, missing, or damaged lug nuts/studs
•Oil/grease leaks from the hub and bearing play

How to prevent it

✓Check for shiny/streaked lug nuts (a loose-wheel tell) on the walk-around
✓Torque wheels after any service and re-torque per schedule
✓Watch hubs for leaks and address bearing noise early

How it affects your CSA

up to 9 pts (fresh)

Severity 3/10. A fresh citation counts at the 3× time weight — up to 9 points toward the Vehicle Maintenance BASIC — then tapers to 2× after 6 months and 1× after a year, dropping off the score at 24 months.

General guidance from the violation’s FMCSA classification — not legal advice, and not a substitute for the inspector’s findings or 49 CFR.

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Challenging 393.70B1II 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 393.70B1II →Read the DataQs guide first

More codes in Vehicle Maintenance

Same BASIC category — ranked by national citation volume

View all Vehicle Maintenance codes →

Other Coupling Devices codes

Codes under the same FMCSA violation group

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Frequently asked questions about 393.70B1II

What does violation 393.70B1II mean?

393.70B1II is the FMCSA roadside-inspection violation code for "Defective / Improper fifth wheel assembly upper half", part of the Coupling Devices group, cited under 49 CFR §393.70B1II.

What BASIC does 393.70B1II affect?

393.70B1II falls under the Vehicle Maintenance BASIC in the FMCSA Safety Measurement System (SMS).

What is the CSA severity weight of 393.70B1II?

393.70B1II carries a severity weight of 3 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 393.70B1II an out-of-service (OOS) violation?

No. 393.70B1II 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 393.70B1II add to a carrier's score?

The point contribution of 393.70B1II depends on its severity weight (3/10) 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.

How can a driver prevent 393.70B1II?

Check for shiny/streaked lug nuts (a loose-wheel tell) on the walk-around; Torque wheels after any service and re-torque per schedule; Watch hubs for leaks and address bearing noise early.

Can 393.70B1II be challenged through DataQs?

Yes. If you believe 393.70B1II 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 393.70B1II Vehicle Maintenance BASIC Carrier CSA lookup CSA glossary

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