What 393.201B means in plain language
When an inspector cites you for 393.201B, they're documenting that one or more bolts securing your cab to the frame are broken, loose, or missing entirely. Your cab—the driver's compartment where you sit—needs to be mechanically sound and firmly attached to the rest of the vehicle. If those bolts fail, the cab can shift, rattle, or in extreme cases separate during operation, creating a serious safety hazard.
This isn't about cosmetic rust or minor vibration. Inspectors are looking for bolts that are visibly absent, obviously corroded through, or so loose they move by hand or exhibit play when the cab is pushed. It's a straightforward structural integrity check: the bolts must be present, intact, and tight enough to keep the cab seated properly on the frame.
What our enforcement data actually shows
Across our database of 13 million+ roadside inspection records, 393.201B is a relatively low-volume violation. In the last 12 months, we recorded 168 citations nationally. Over the last 90 days, enforcement was steady at 36 citations. All-time, the code ranks #1104 out of 3,036 FMCSR codes by citation frequency.
What matters most for your situation: the out-of-service (OOS) rate for 393.201B is 5.9%—meaning only 17 out of 269 trucks cited were actually removed from service. This is dramatically lower than the all-FMCSR average OOS rate of 31.4%, indicating that inspectors typically view this as a correctable defect rather than an immediate safety-critical failure. You are unlikely to be placed out of service on the spot, though the citation itself will appear on your record.
The last 90 days show the citation trend is active but not spiking. In March 2026, inspectors issued 12 citations with 0 OOS placements. In February, 20 citations with 1 OOS. This suggests the violation is caught consistently but only rarely deemed severe enough to halt operations.
Who gets cited most
Our data from the last 180 days shows three states leading in 393.201B enforcement:
- Illinois: 42 citations, 1 out-of-service (2.4% OOS rate)
- Texas: 28 citations, 3 out-of-service (10.7% OOS rate)
- New Mexico: 9 citations, 0 out-of-service (0.0% OOS rate)
Texas shows a notably higher OOS rate (10.7%) compared to Illinois (2.4%)—a difference of over 8 percentage points. If you operate in Texas, inspectors there appear more inclined to treat loose cab bolts as a reason to take the truck out of service. Illinois inspectors cite the violation more often overall but rarely escalate to OOS.
No single carrier dominates this violation. Our all-time data shows fleets such as Ridol Inc (USDOT 299458) and Lafrieda Veal and Lamb Co Inc (USDOT 1517306) with 3 citations each, and several carriers with 2 citations. This is not a pattern confined to any particular fleet type or size—the violation is spread across diverse operations.
How severe is this compared to similar codes
393.201B sits in the Vehicle Maintenance category alongside codes like inoperable lamps, brake defects, and frame damage. Here's how it compares:
- 393.9 (Inoperable Required Lamp): 180,097 all-time citations, 6.9% OOS rate. Cab bolt tightness (393.201B) is cited far less often but at nearly the same OOS rate, suggesting similar risk perception by enforcement.
- 393.11 (Lighting Devices/Reflectors): 179,734 citations, 1.8% OOS rate. This is cited more frequently and has a lower OOS rate, making it a more routine defect.
- 396.3(a)(1) (Inspection/Repair/Maintenance—General): 236,919 citations, 45.3% OOS rate. This is a much broader code with far higher enforcement pressure and OOS severity.
In context, 393.201B is a low-frequency, low-severity maintenance code. It's cited less often than lighting violations and almost never results in an immediate shutdown.
How to avoid it
Look at what co-occurs with 393.201B citations to understand what inspectors see when they flag loose cab bolts. In the last 90 days, the most common simultaneous violations were:
- 393.9 (Inoperable Lamp): 14 shared inspections
- 393.95A & 393.95F (Emergency Equipment): 5 shared each
- 393.201A (Frame Damage): 4 shared inspections
This pattern tells you that loose cab bolts often appear during comprehensive vehicle inspections where other structural or electrical defects are already present. A truck with one maintenance gap tends to have others.
Driver-actionable prevention steps:
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Pre-trip cab inspection: Walk around your cab after parking. Look underneath the driver and passenger sides where the cab meets the frame. Feel for any visible gaps between the cab body and frame. Push down on the cab corners with your hands—it should not shift or rock relative to the frame. Modern cabs should be tight enough that you sense no movement.
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Check after rough roads or accidents: After driving over rough terrain or any impact, do a quick visual of the cab bolts. Road vibration can loosen fasteners over time, especially if they weren't torqued correctly during the last service.
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Include cab mounting in your service routine: When your truck is in the shop for preventive maintenance, explicitly ask the technician to inspect and torque all cab-mounting bolts. This is not a major repair—it's a 15-minute job on most vehicles—and catching loose bolts before an inspector does saves you a citation and potential roadside delays.
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Know your vehicle make: Our enforcement data shows Freightliner (81 all-time citations) and International (41 citations) are the most commonly cited for this defect. If you drive one of these makes, add cab-mounting checks to your monthly inspection routine, as these platforms may have particular bolt-loosening characteristics.
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Avoid stacking violations: Since 393.201B often appears alongside lighting and emergency equipment issues, maintain your lamps and carry complete emergency equipment. A truck in good overall condition is less likely to be subjected to the detailed scrutiny that exposes a loose cab bolt.