393.55 Violation: What It Means and How to Fix It
Data through September 24, 2026 · Last updated October 28, 2026 · By Chad Griffith, founder
Quick Answer
393.55 (Antilock brake systems) was cited 58,166 times in roadside inspections of interstate for-hire carriers with 5 to 50 trucks from September 25, 2024 to September 24, 2026, and 0.0% of those citations put the driver or vehicle out of service. The most common version is 393.55E-B: Air Brake - ABS malfunction lamp defective on trailers manufactured on or after March 1 1998.
58,166
Citations on carriers with 5 to 50 trucks
0%
Out of service
283,054
All carriers, same period
What the rule says
Trucks and trailers built after the ABS dates in the rule must have a working antilock brake system and malfunction indicator lamp (49 CFR 393.55).
When it puts you out of service
ABS lamp violations are not out of service (0.0% here), but they are among the most cited vehicle codes on small carriers.
The codes on the inspection report
| Code | What the officer wrote | Severity weight | Citations, 5 to 50 trucks | Out of service |
|---|---|---|---|---|
| 393.55E-B | “Air Brake - ABS malfunction lamp defective on trailers manufactured on or after March 1 1998” | 4 | 26,371 | 0.0% |
| 393.55E | “No or Defective ABS Malfunction Indicator Lamp for trailer manufactured after 03/01/1998” | 4 | 6,920 | 0.0% |
| 393.55C1-B | “Air Brake - Truck-tractor manufactured on or after March 1 1997 not equipped with an ABS system. System does not function or indicates a fault.” | 4 | 5,316 | 0.0% |
| 393.55D1-B | “Air Brake - ABS malfunction lamp defective on truck-tractor manufactured on or after March 1 1997 and each single unit CMV on or after 1998.” | 4 | 3,827 | 0.0% |
| 393.55D2-B | “Air Brake - ABS malfunction lamp defective on truck-tractor manufactured on or after March 1 2001 for towed vehicle.” | 4 | 3,806 | 0.0% |
| 393.55C2-B | “Air Brake - CMV other than truck-tractor manufactured on or after March 1 1998 not equipped with an antilock brake system. System does not function or indicates” | 4 | 3,194 | 0.0% |
| 393.55C1 | “Truck Tractor manufactured on or after March 1 1997 not equipped with an antilock brake system” | 4 | 3,003 | 0.1% |
| 393.55D3 | “No or Defective ABS Malfunction Indicator for towed vehicles on vehicles manufactured after February 2001” | 4 | 1,885 | 0.0% |
| 393.55C2 | “CMV other than truck-tractor manufactured on or after March 1 1998 not equipped with an antilock brake system” | 4 | 1,568 | 0.0% |
| 393.55D1 | “CMV not equipped with ABS malfunction circuit or signal (Truck-Tractor mfg on/after 3/1/1997; Straight Truck mfg on/after 3/1/1998)” | 4 | 714 | 0.6% |
| 393.55D2 | “CMV manufactured on/after 3/1/2001 not equipped with ABS malfunction circuit / lamp from towed vehicle in cab” | 4 | 700 | 0.0% |
| 393.55B-B | “Hydraulic Brake - ABS malfunction lamp defective on truck/bus manufactured on or after March 1 1999” | 4 | 291 | 0.0% |
How it scores (violation points)
How it scores: in FMCSA's Safety Measurement System each violation counts its severity weight, plus 2 if it put the driver or vehicle out of service, times 3 in its first 6 months, 2 from 6 to 12 months, and 1 from 12 to 24 months. FMCSA has approved a simpler scale that is not live yet.
How to fix it
- Read the ABS fault code and repair the sensor, wiring or module; replacing the bulb alone does not clear a real fault.
- Check that the trailer ABS lamp lights at key-on and goes out, on every trailer you pull.
Stop it happening again
- Add the ABS lamp key-on check to the pre-trip inspection.
Challenging it in DataQs
Use DataQs (dataqs.fmcsa.dot.gov) only when the report is wrong: the wrong carrier or vehicle, a violation that did not happen, or a citation a court dismissed without a fine or found you not guilty of, which removes it from the Safety Measurement System; a conviction of a different charge lowers its weight to 1 (FMCSA adjudicated citations policy). Fixing the defect afterward is not a reason to remove it; keep the repair record instead.
FileFlo reads your public FMCSA record, lists every violation with the rule behind it, and keeps the driver and vehicle records that stop repeats.
Run it yourself: the Audit-Ready Setup, $499 through December 31, 2026, then $199 a month for up to 15 trucks. Or FileFlo runs it: $1,500 a month for up to 15 trucks, Setup included, and your first month back if you are not happy.
About these numbers
Counts are violations cited in roadside inspections used in FMCSA's Safety Measurement System from September 25, 2024 to September 24, 2026 (dataset 8mt8-2mdr on data.transportation.gov, October 2026 run). Carriers with 5 to 50 trucks means 66,936 active interstate for-hire carriers with 5 to 50 power units and more trucks than buses, based in the 50 states or DC, from FMCSA's census file. This is FileFlo's reading of public FMCSA data, not an FMCSA rating. Severity weights are the current SMS weights.