What 393.48A means in plain language
FMCSR 393.48A covers a straightforward situation: one or more of your commercial motor vehicle's brakes are not working correctly or have failed in some way. That could mean a brake that provides no stopping force at all, or one that's degraded enough that an inspector flags it as defective. The regulation doesn't require every single brake to have failed — just one is enough to draw a citation.
This matters because brakes are the last line of defense between your rig and a serious crash. Inspectors are trained to check brake stroke, adjustment, lining condition, and hardware integrity during Level I and Level II inspections. A defect that might seem minor in a shop can look very different on a roadside inspection report.
If you've just received this citation, understand that 393.48A is distinct from the out-of-service brake standards that require 20% or more of your brakes to be defective before you're parked. A single defective brake under 393.48A may not put you out of service, but it will follow you into your CSA safety score.
What our enforcement data actually shows
Across our 13 million+ inspection records, 393.48A has accumulated 26,907 all-time citations, placing it at #103 out of 3,036 FMCSR codes by citation volume — firmly in the top 3.4% of all cited regulations. That's not a niche code; it's one inspectors reach for regularly.
Enforcement has been heavy recently. Our inspection records show 17,052 citations in the last 12 months and 3,831 in just the last 90 days, which means this code is being written at a pace of roughly 1,277 citations per month. Looking at the monthly trend, October 2025 was the single busiest month with 1,643 citations, and February 2026 came in close behind at 1,743 citations — the highest single month in the trailing 12-month window.
On the out-of-service question: 393.48A is not OOS-eligible as a standalone trigger, and the numbers bear that out. Of 26,907 all-time citations, 2,585 resulted in an OOS order — a 9.6% OOS rate. Compare that to the all-FMCSR average OOS rate of 31.4%, and this code sits well below the norm. That said, 2,585 trucks were still parked, and an OOS order on your record compounds CSA points significantly. The low OOS rate does not mean inspectors are lenient; it means most 393.48A citations are written without parking the vehicle, but the violation still scores against you.
The CSA severity weight for 393.48A is 8 out of a possible 10. That's a heavy hit on your Unsafe Driving and Vehicle Maintenance BASIC scores, and it stays on your record for 24 months.
Who gets cited most
Looking at the last 180 days, Texas dominates with 6,969 citations — by a wide margin. Iowa comes in second at 407 citations, and Illinois third at 362 citations. The OOS rate variation across these states is striking: Texas runs at 6.9%, Iowa at 3.9%, while Illinois reaches 23.8%. That's a nearly 20-percentage-point spread between Iowa and Illinois, which tells you that the same violation can have very different enforcement outcomes depending on where you're stopped. If you're running Illinois lanes, be aware that inspectors there are putting trucks out of service for this code at more than three times the rate seen in Texas.
Our data shows fleets such as ACME TRUCK LINE INC (USDOT 52767) with 79 all-time citations and SUPLICIUM TRANSPORT LLC (USDOT 4381255) with 43 citations appear at the top of the carrier list. High citation counts at any carrier generally reflect high inspection exposure combined with recurring maintenance gaps — and they draw heightened scrutiny from inspectors who can see carrier history on their tablets.
On the vehicle side, Freightliner (FRHT) accounts for 6,363 all-time citations under this code, followed by Kenworth (KW) at 3,101 and Peterbilt (PTRB) at 2,446. These are the most common tractors on U.S. highways, so the volume reflects fleet size — but if you're driving one of these makes, know that inspectors have plenty of pattern recognition on what defects look like on your specific brake hardware.
How severe is this compared to similar codes
Within the Vehicle Maintenance category, 393.48A's 26,907 citations look modest against some peers, but its severity weight keeps it dangerous for your CSA score. Consider 393.9(a) — Inoperable Required Lamps — which has 660,737 all-time citations at a 15.4% OOS rate. That code is written far more often, but its OOS rate of 15.4% is actually higher than 393.48A's 9.6%, meaning a lamp violation is more likely to park you than a single defective brake.
On the other end, 396.3(a)(1) — the general Inspection, Repair, and Maintenance code — shows 236,919 citations and a 45.3% OOS rate. That code is nearly nine times as likely to result in an out-of-service order. If your 393.48A citation is accompanied by a 396.3(a)(1) write-up, your risk of being placed OOS escalates sharply.
Also worth noting: 393.47E (Slack Adjuster Defective) shows 180,363 citations at a 0.0% OOS rate in our database — a brake-related code that almost never parks a truck on its own, but which appears alongside 393.48A in 572 shared inspections in the last 90 days alone. If your slack adjusters are out, a defective brake citation usually isn't far behind.
How to avoid it
The co-occurring code pattern in our data points clearly at what gets missed before drivers leave the yard. Use these checks every pre-trip:
- Walk every brake chamber and check pushrod stroke visually. With 393.47E (Slack Adjuster Defective) appearing in 572 shared inspections alongside 393.48A in the last 90 days, out-of-adjustment slack adjusters are the most direct path to this citation. Automatic slack adjusters still need to be checked — they fail without warning.
- Squeeze the brake lines and inspect tubing at each axle. 393.45B2UV (Brake Tubing/Hoses Inadequate) co-occurred in 521 shared inspections over the last 90 days. A cracked, abraded, or improperly supported hose will cause a brake to perform defectively under hard application.
- Check all required lamps before pulling out. 393.9 (Inoperable Required Lamp) appeared in 801 shared inspections in the same 90-day window. Inspectors who stop you for a lamp defect will check brakes. Fix the obvious items so you don't invite a full Level I.
- Verify your periodic inspection documentation is on the truck. 396.17C (No Proof of Periodic Inspection) appeared in 353 shared inspections. A missing annual inspection sticker signals to an inspector that maintenance has been neglected and often triggers a deeper look at brake hardware.
- Inspect steering components at every pre-trip. 393.53B (Steering System Components Worn) co-occurred in 594 inspections. Steering and brake defects are discovered together because inspectors examine the whole underside once they're under the vehicle.
- If you drive a Freightliner, Kenworth, or Peterbilt, pay particular attention to S-cam bushing wear and foundation brake hardware. Our data shows these makes account for more than 11,900 combined citations under 393.48A, and worn bushings are a common root cause that drivers can feel as brake pull or sponginess before a defect is formally flagged.