What 393.71K-CDLSC means in plain language
A fifth wheel is the coupling mechanism that connects your tractor to a semi-trailer. This code flags a fifth wheel assembly that is defective, has excessive wear, or is not properly secured to the frame.
This isn't a minor cosmetic issue. The fifth wheel bears the full weight and dynamic forces of your loaded trailer as you accelerate, brake, and corner. If it fails, your trailer can separate from your tractor—a catastrophic failure that endangers you, your cargo, and everyone around you. Inspectors are looking for visible cracks, missing or broken locking mechanisms, loose mounting bolts, or wear that compromises the structural integrity of the coupling.
This code applies to any defect in the fifth wheel assembly itself, not the king pin or landing gear (which have their own codes). The focus is on the metal plate and locking jaw that clamp onto the king pin.
What our enforcement data actually shows
Across our 13 million roadside inspection records, 393.71K-CDLSC citations are extremely rare. We see only 2 all-time citations for this code, with 1 citation in the last 90 days and 2 in the last 12 months. Despite the low citation volume, this code ranks #2651 of 3,036 FMCSR codes by enforcement frequency.
The enforcement severity is high: our inspection records show a 100.0% out-of-service rate for this code. Every time an inspector has cited it, the vehicle was placed out of service. This is dramatically higher than the all-FMCSR average OOS rate of 31.4%, underscoring how seriously inspectors treat fifth wheel defects. When an inspector finds a defective fifth wheel, they will not allow the vehicle to continue operating.
In the last 90 days, 1 citation was recorded. Over the last 12 months, the data shows 2 citations total, indicating this violation occurs sporadically but with absolute enforcement consequences.
Who gets cited most
Our inspection records show Pennsylvania with 1 citation in the last 180 days, resulting in a 100.0% out-of-service rate. With such limited enforcement volume nationally, state-level variation is not meaningful—what matters is that wherever this citation occurs, the vehicle is immediately removed from service.
By carrier, our data shows fleets such as D & K GRAHAM TRUCKING INC (USDOT 351962) and NBARAHONA TRUCKING LLC (USDOT 4026127) with 1 citation each across our entire database. These figures reflect isolated events, not systemic patterns.
By vehicle make, PTRB-branded equipment appears in 2 of the citations in our all-time records, with LUFK and WLKR each appearing once. This distribution is too sparse to indicate a model-specific defect pattern.
How severe is this compared to similar codes
Within the Vehicle Maintenance category, fifth wheel defects occupy a unique enforcement position due to their safety criticality. Compare this to peer codes:
- 393.9(a) — Inoperable required lamps: 660,737 citations with a 15.4% OOS rate. Lamp failures are far more common and much less likely to result in out-of-service status.
- 396.3(a)(1) — Inspection/repair/maintenance general: 236,919 citations with a 45.3% OOS rate. This broader maintenance code is cited frequently and results in OOS about 45% of the time.
- 393.47E — Slack adjuster defective: 180,363 citations with a 0.0% OOS rate. Brake slack adjuster issues, while common, are rarely grounds for immediate out-of-service removal.
The 100.0% OOS rate for fifth wheel defects reflects their safety-critical role. Unlike lighting or slack adjusters, a failed fifth wheel can cause loss of vehicle control and trailer separation. Inspectors treat them as non-negotiable.
How to avoid it
The rarity of this citation suggests that most drivers and fleets maintain their fifth wheels adequately. However, the 100% out-of-service consequence makes prevention essential. Our co-occurring violation data shows that fifth wheel citations sometimes appear alongside frame defects (393.201A-FR and 393.201B-FR) and brake system issues (393.43A-TSV), indicating that structural integrity inspections are critical.
Before you hit the road, inspect your fifth wheel assembly:
- Look for visible cracks or breaks in the main casting and locking jaw. Run your hand (carefully) along the underside and sides of the fifth wheel to feel for cracks you might miss visually.
- Check all mounting bolts and fasteners that connect the fifth wheel to the frame. They should be tight with no play. Loose bolts are a direct pathway to this citation.
- Verify the locking mechanism works smoothly—the jaws should close completely and lock the king pin with a firm, audible click. No hesitation or grinding.
- Examine the top and bottom wear surfaces where the king pin rides. Excessive wear that creates gaps or play means the coupling is failing.
- Inspect the frame around the fifth wheel mount for cracks, bending, or separation. The frame attachment points must be solid.
- Test the release lever and lock pin to ensure they function without resistance. If you feel grinding or hear unusual sounds, stop and get it inspected.
Most importantly: do not ignore unusual sounds or vibrations from the fifth wheel area while driving. If you suspect a problem, find a safe place to stop, get out, and look. A few minutes of inspection can prevent a catastrophic failure that puts your life and others at risk.
Regular pre-trip inspections—conducted every time you hook up—are your best defense. The fifth wheel is checked as part of any formal CVSA inspection; make sure you're checking it with the same rigor before an inspector does.