What 393.50D-B means in plain language
FMCSR 393.50D-B addresses steering system defects on commercial motor vehicles. The regulation requires that your steering mechanism be in proper working order—not broken, not damaged, and functioning as designed. This covers everything from the steering wheel connection through the linkage, tie rods, drag links, and steering column that ultimately control your front wheels.
When an inspector cites you for 393.50D-B, they've identified something physically wrong with how your steering system operates. This could be excessive play in the steering wheel, bent or cracked steering components, loose bolts or fasteners in the steering linkage, or damage that compromises steering responsiveness. The core issue is safety: if your steering doesn't work reliably, you cannot control the vehicle predictably.
Importantly, this citation does not automatically take your truck out of service. Our inspection records show it is not an OOS-eligible violation, meaning inspectors cite it but do not remove the vehicle from the road on the spot. However, it still carries weight in your safety profile and must be corrected.
What our enforcement data actually shows
Across our 13 million+ inspection records, 393.50D-B has been cited 179 times all-time, with 110 citations in the last 12 months and 19 in the last 90 days. The code ranks #1246 out of 3,036 FMCSR codes by citation volume—relatively uncommon compared to widespread violations like inoperable lamps.
The critical enforcement fact: our data shows a 0.0% out-of-service rate for 393.50D-B across all 179 all-time citations. This stands in sharp contrast to the all-FMCSR average OOS rate of 31.4%. None of the vehicles cited for steering mechanism defects in our database were placed out of service. This tells you that inspectors treat this as a correctable defect rather than an immediate roadworthiness emergency—but it also means you must address it promptly to avoid escalation or repeated violations.
Monthly trends over the last 12 months show steady citation activity, with May 2025 recording the highest month at 12 citations and several months in the 6–9 range. This suggests steering inspections occur regularly but without seasonal spikes.
Who gets cited most
Our enforcement data shows California leads all states with 19 citations in the last 180 days, followed by interstate/unlisted states with 15 citations, and Pennsylvania with 5 citations. All three maintain a 0.0% OOS rate, consistent with the national pattern for this code. Kentucky, Ohio, South Carolina, Utah, Georgia, and Kansas each recorded 1 citation with no OOS placements.
On the carrier side, our data shows fleets such as Oak Harbor Freight Lines Inc with 4 citations, Supor Trucking LLC with 3 citations, and nine other carriers with 2 citations each. No carrier pattern emerges suggesting systematic steering maintenance issues—these are isolated citations distributed across the industry.
Vehicle make data is more revealing: Freightliners dominate the citation list, with 39 Freightliner citations all-time, followed by 19 Freightliner (alternate designation), 14 Utility vehicles, 13 International, and 12 Peterbilt. This distribution reflects the market prevalence of these makes in trucking rather than a defect trend specific to one manufacturer.
How severe is this compared to similar codes
393.50D-B falls within the Vehicle Maintenance category alongside codes like 393.9 (Inoperable Required Lamp), which has generated 180,097 citations with a 6.9% OOS rate, and 393.11 (Lighting devices/reflectors) with 179,734 citations and a 1.8% OOS rate. Both of these far exceed 393.50D-B in citation volume.
A closer peer is 393.47E (Slack adjuster defective), which has 180,363 citations and a 0.0% OOS rate—identical to 393.50D-B's enforcement profile. This suggests that brake and steering system defects are treated similarly: cited, correctable, but not automatic roadside removals.
In terms of CSA Severity Weight, 393.50D-B carries a weight of 8, placing it in the moderate-severity range. This means it contributes measurably to your SMS (Safety Management System) score if it accumulates, so a single citation today is manageable but repeated violations harm your safety record.
How to avoid it
Steering mechanism defects are almost entirely preventable through disciplined pre-trip inspection. Here is what our data tells you to focus on:
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Check for play and binding. Grab the steering wheel and rock it gently side to side while the engine is off. More than a half-inch of movement before the wheels respond indicates wear in the steering linkage. Turn the wheel lock to lock and listen for grinding, clicking, or resistance that suggests bent tie rods or damaged steering arms.
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Inspect visible steering components. Walk around the front end and look directly at the tie rods, drag links, and steering column. Look for bends, cracks, missing hardware, or visible damage. Our co-occurring violation data shows that steering defects sometimes appear alongside brake and coupling defects, suggesting vehicles with one maintenance gap may have others; a thorough walk-around catches multiple issues.
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Look for loose bolts and fasteners. Steering linkage relies on tight connections. Spin the vehicle through a parking lot and feel for vibration or vague steering response. Loose fasteners at the pitman arm, tie rod ends, or steering column mounts will cause excessive play.
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Check steering fluid (if power steering equipped). Low or contaminated power steering fluid can cause sluggish or unpredictable steering response. Top it off during your pre-trip and look for leaks around the pump or hoses.
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Verify steering column security. Confirm the steering column is solidly mounted to the frame and does not move or rattle when you apply force. A loose column affects steering control and safety.
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Don't drive past symptoms. If steering feels vague, unresponsive, or requires excessive effort, report it to dispatch before the next inspection. Fixing it proactively prevents a citation and keeps your vehicle roadworthy.
Our inspection records show steering defects are cited but not treated as emergency out-of-service violations—meaning you have time to correct them. That said, one citation establishes a violation record. If you're cited twice in 12 months for steering issues, regulators and insurance carriers will see a pattern of deferred maintenance. Your safest move is to address any steering concern immediately and document the repair.