FMCSR 393.47(b) — Brake Actuators/Chambers Defective: Driver FAQ

Yes — at a very high rate. Even though 393.47(b) is not automatically OOS-eligible on paper, our inspection records show that 2,466 of the 3,181 all-time citations under this code resulted in an out-of-service order. That works out to a 77.5% OOS rate — more than double the all-FMCSR average of 31.4%. In practical terms, if an inspector finds defective brake actuators or chambers, the odds are heavily stacked toward parking your truck on the spot. Do not assume a non-OOS-eligible label means you will keep rolling.

393.47(b) carries a severity weight of 7 on the FMCSA CSA scale, which places it in the upper tier of vehicle maintenance violations. The actual points that hit your Safety Measurement System (SMS) record are multiplied based on how recently the inspection occurred — violations within 6 months count the most. Points begin dropping off at the 12-month mark and fall further at 24 months. Because this code sits in the Vehicle Maintenance BASIC, the points follow the carrier's DOT number. Drivers with a CDL should note the inspection will also appear tied to their record.

Get the brakes inspected and repaired by a qualified mechanic before the truck moves under load. Here are the concrete steps:

1. If placed OOS: Do not move the vehicle until a certified brake technician signs off on the repair.
2. Document everything: Get a dated, itemized repair invoice that identifies the specific actuator or chamber replaced.
3. Notify your fleet safety manager immediately — this code has a 77.5% OOS rate across 3,181 citations, so it will draw attention.
4. Request a re-inspection to clear the OOS order if one was issued.
5. File the paperwork — keep copies of the repair for any future DataQs challenge.

Very serious — its OOS rate dwarfs nearly every peer code in the Vehicle Maintenance category. Across our inspection database, the all-FMCSR average OOS rate is 31.4%. A closely watched peer code, 396.3(a)(1) (general maintenance), carries a 45.3% OOS rate. 393.47(b) comes in at 77.5% — nearly 2.5 times the FMCSR average. By comparison, 393.47E (slack adjuster defective) shows a 0.0% OOS rate across 180,363 citations, and 393.9(a) (inoperable lamps) sits at 15.4% across 660,737 citations. Defective brake actuators are treated by inspectors as an immediate safety threat, not a paperwork issue.

Yes, you can submit a challenge through FMCSA's DataQs system (Request for Data Review). Because 393.47(b) is an equipment finding — not a missing document — a successful challenge typically requires showing that the inspector's observation was factually wrong, that the component cited was functional and met standards, or that the violation was recorded in error. Gather your pre-trip inspection log, any maintenance records predating the stop, and the repair invoice if work was done. Submit through the DataQs portal at ai.fmcsa.dot.gov/DataQs. If the challenge is upheld, the citation is removed from your SMS record entirely.

The top states in our inspection records for 393.47(b) citations are not broken out by state in the current dataset. The statistics block for this code tracks top carriers and vehicle makes but does not include a state-by-state breakdown for 393.47(b) specifically. What we can say is that the 3,181 all-time citations span a wide carrier mix including cross-border operators, suggesting enforcement is not concentrated in a single region. Check TruckCodex's full inspection search to filter 393.47(b) citations by state in real time.

It cannot wait. The data is unambiguous: 77.5% of all 393.47(b) citations across 3,181 inspections ended with the vehicle placed out of service. That is not a nuisance violation — it reflects inspectors consistently judging defective brake actuators as an immediate roadway hazard. Additionally, the code carries a CSA severity weight of 7, meaning it adds significant points to the Vehicle Maintenance BASIC quickly. With zero citations recorded in the last 90 days, enforcement may be cyclical, but the OOS rate signals that when inspectors do find this defect, they act on it almost every time. Repair before the next trip, not before the next PM.

It attaches to both, but in different ways. Under FMCSA's CSA methodology, a vehicle maintenance violation like 393.47(b) — with its severity weight of 7 — counts against the carrier's Vehicle Maintenance BASIC score, tied to the carrier's DOT number. The roadside inspection record also links to the driver's inspection history through their CDL or identification on the inspection report. Carriers are the primary target for SMS interventions based on Vehicle Maintenance BASIC scores, but drivers accumulate an inspection history that prospective employers and safety auditors can review.