Parts and accessories violations consistently rank among the top reasons inspectors place Commercial Motor Vehicles out of service. These violations are more than mechanical oversights, they directly affect road safety, vehicle integrity, and FMCSA compliance scores.
For fleet owners, CDL drivers, and motor carriers, ignoring even one defective part can lead to fines, failed inspections, and a damaged CSA score.
Parts and accessories violations (49 CFR Part 393) appear in nearly every roadside inspection because they cover a wide range of essential safety equipment, including lighting, brakes, tires, fire extinguishers, reflective devices, and warning systems.
This blog breaks down each major violation from the official FMCSA list, explains what the regulation means, why it is commonly cited, and how to prevent it.
Not Having Required Operable Lamps – 49 CFR 393.9
One of the most frequently cited violations during DOT roadside inspections is the absence of required lamps or having defective lighting equipment. Regulation 393.9 states that all lamps and reflective devices must be operable at all times when the commercial vehicle is in use. This includes headlights, tail lamps, brake lamps, turn signals, clearance lamps, identification lamps, and side marker lights.
The reason this violation appears so often is simple. Lighting devices are exposed to weather, road debris, vibrations, and electrical wear, making them prone to failure. A single burned-out bulb may seem minor to a driver, but under FMCSA rules, it is considered a safety risk because other motorists rely on visual cues to understand a truck’s movement. Lack of proper lighting reduces visibility at night, compromises signaling, and dramatically increases accident risk.
The simplest solution is strict adherence to the mandated 392.7(a) pre-trip inspection, along with weekly maintenance checks. Fleet operators should also adopt a preventive electrical-system inspection plan to catch loose wires, moisture damage, and blown fuses.
Lighting violations are avoidable with proper oversight, yet they contribute heavily to CSA scores. Implementing automated maintenance reminders through our Fleet Compliance Management Software ensures lights are checked, documented, and compliant before every trip.
3. Clamp/Roto-Chamber Type Brake(s) Out of Adjustment – 49 CFR 393.47(e)
The FMCSA considers brake adjustment issues to be a critical safety violation. Regulation 393.47(e) covers clamp-style and roto-chamber brake designs that must maintain proper adjustment to ensure adequate stopping power. When brakes fall out of adjustment, the braking force is reduced, increasing stopping distance and raising the risk of brake failure.
Most out-of-adjustment violations are discovered during CVSA Level I inspections where inspectors measure the brake pushrod stroke length. If it exceeds the allowable limit, the vehicle is immediately marked out of service. The underlying cause often relates to worn components, malfunctioning automatic slack adjusters, or lack of proper maintenance.
In our field experience working with fleets nationwide, we’ve seen that even trucks equipped with automatic slack adjusters can fail if they are not routinely lubricated or if drivers excessively brake, causing thermal expansion and misalignment. The FMCSA also cites 393.53(b) for automatic brake adjuster violations, meaning if your truck uses automatic adjusters, they must function correctly.
A strong fleet compliance program includes scheduled brake inspections every 90 days and mandatory mechanic verification logs.
Tire Tread Depth Less Than 2/32 Inch – 49 CFR 393.75(c)
Tires are one of the most critical safety components on any CMV. Regulation 393.75(c) states that commercial vehicles must not operate with tires having a tread depth less than 2/32 of an inch on the steering axle or any other position. Low tread depth reduces traction, especially in wet or snowy conditions, and increases the chance of blowouts.
During inspections, FMCSA officers use a tread gauge to measure depth at the major grooves. If even one spot falls below the required depth, the violation is recorded.
FMCSA treats tread-depth violations seriously because worn tires significantly affect braking and handling. If a tire is excessively worn or has exposed belts, inspectors may place the vehicle out of service. Fleets with older trailers also see higher tire violations because trailers are often overlooked in maintenance routines.
To prevent this, fleets should adopt weekly tire inspections, track tire age, and log rotations through digital fleet management systems. Drivers should be trained to identify uneven wear, sidewall damage, and hotspots. Maintaining compliant tread depth not only prevents DOT violations but also protects drivers and improves fuel efficiency.
No/Discharged/Unsecured Fire Extinguisher – 49 CFR 393.95(a)
FMCSA regulation 393.95(a) mandates that all commercial vehicles must carry an ABC-type fire extinguisher with at least a 5-B:C rating and that it must be fully charged, accessible, and securely mounted. Fire extinguisher violations remain extremely common, mainly because extinguishers lose pressure over time or drivers fail to verify their condition during pre-trip checks.
In many cases, fleets purchase extinguishers but fail to implement a regular inspection schedule. Without monitoring, extinguishers gradually leak pressure, leading to discharge or non-operational status. Additionally, many drivers simply place the extinguisher inside a cab compartment without properly securing it, resulting in a compliance violation even if the extinguisher works.
During DOT inspections, officers verify three requirements:
- The extinguisher is present
- It is fully charged
- It is securely mounted and readily accessible
Failing any one of these leads to violation entry. For hazmat carriers, extinguisher requirements are even more strict under Part 397.
A proper fire-safety compliance plan should include monthly pressure checks, annual professional recertification, and digital logs.
No/Defective Lighting, Reflectors, Projected Devices – 49 CFR 393.11
Under regulation 393.11, CMVs must have reflective devices, lamps, mounted reflectors, and projected lighting devices installed and functioning as required. This includes red and amber reflectors, reflective tape, rear identification lamps, side reflectors, and conspicuity markings.
Reflective devices are essential for nighttime visibility and accident prevention, especially when trucks are parked on the roadside or backing up. Many fleets violate this rule because reflective tapes wear out over time, get covered in dirt, or peel due to weather damage. Additionally, older trailers often contain outdated reflectors that no longer meet reflectivity standards.
DOT inspectors examine whether reflectors are clean, unbroken, unobstructed, and placed in the correct positions as outlined in the Federal Motor Vehicle Safety Standards (FMVSS 108). Missing or cracked reflectors result in violations. If a vehicle lacks required rear identification lamps or reflective tape, inspectors consider the vehicle unsafe.
Fleets should perform quarterly conspicuity inspections and replace worn reflective tape immediately. SafeRoad Compliance trains drivers to document reflector conditions during pre-trip inspections to avoid repeat violations.
Conclusion:
Parts and accessories violations under 49 CFR Part 393 remain some of the most commonly cited issues in FMCSA inspections, not because fleets don’t care about safety, but because these components experience frequent wear and require consistent attention.
Every lamp, reflector, brake component, tire, and safety device plays a crucial role in preventing accidents, improving visibility, and keeping commercial vehicles road-ready.
For trucking companies and fleet owners, these violations can seriously impact CSA scores, increase insurance costs, and result in costly downtime. But the good news is that almost all of these issues are 100% preventable with proper maintenance, documentation, and training.
SafeRoad Compliance helps fleets stay ahead by providing real-time monitoring, automated maintenance reminders, driver training, and expert DOT compliance support, ensuring your vehicles meet FMCSA standards at every checkpoint.
With the right tools and proactive compliance management, your fleet can stay operational, safe, and fully audit-ready year-round.
Key Takeaways
- Parts and accessories violations are among the most frequently cited DOT issues and directly impact CSA scores.
- Lighting violations, under 393.9 and 393.11, are the top offenders due to exposure to weather, debris, and electrical wear.
- Brake out-of-adjustment violations under 393.47(e) are considered a severe safety risk and often result in out-of-service orders.
- Tire tread depth violations under 393.75(c) remain common due to poor inspection habits, underinflation, and misalignment.
- Fire extinguishers must be charged, secured, and accessible to avoid violations under 393.95(a).
- Regular inspections, preventive maintenance, and detailed documentation drastically reduce violation risks.
- SafeRoad Compliance offers fleet management, DOT audit support, and compliance monitoring to help fleets avoid penalties and operate with confidence.
Frequently Asked Questions (FAQs)
These violations relate to required safety equipment such as lamps, brakes, tires, reflectors, fire extinguishers, and other essential components. FMCSA mandates these items to ensure vehicle safety and visibility.
Very serious. Many violations can increase CSA scores, trigger DOT audits, result in out-of-service orders, or lead to expensive fines.
Lighting equipment is exposed to harsh conditions and often fails due to moisture, vibration, corrosion, and poor electrical connections. Lack of routine inspections worsens the problem.
Schedule brake inspections every 90 days, ensure automatic slack adjusters are properly lubricated, and train drivers to recognize early brake issues.
FMCSA requires a minimum of 2/32 inch tread depth across most positions. Anything less results in a violation.
Yes. CMVs must carry an ABC extinguisher that is fully charged and securely mounted as per 393.95(a).
Absolutely. With consistent inspections, preventive maintenance, and proper documentation, fleets can avoid almost all Parts and Accessories Violations.
