NHTSA has closed Preliminary Evaluation PE25015 into loss of braking force on 2019–2020 Acura ILX vehicles, citing Honda’s earlier Recall 25V859 as adequate resolution. The Office of Defects Investigation opened the probe last October after consumer complaints alleging master cylinder failures that caused soft pedal feel or the pedal traveling intermittently to the floor. Honda’s recall, which replaces the master cylinder with a unit using a different cup-seal material, covers a broader 2016–2020 model-year range than the investigation’s original scope. NHTSA reserved the right to take further action if circumstances warrant.
Highlights
- ODI opened PE25015 on October 23, 2025, after receiving complaints of master cylinder failures on 2019–2020 model-year Acura ILX vehicles.
- Honda traced the defect to residual plasticizer in the brake reservoir hose contaminating the brake fluid, which swelled the secondary cup seal and allowed fluid to bypass during pedal application.
- Recall 25V859 covers 70,658 Acura ILX vehicles produced October 9, 2014 through January 29, 2020 — a broader range than PE25015’s 2019–2020 scope.
- Remedy is master cylinder replacement with a redesigned inner cup seal using a different material for improved sealing.
What the Investigation Found
PE25015 was prompted by Vehicle Owner Questionnaires alleging that brake pedals could travel to the floor with a loss of braking force on 2019–2020 Acura ILX vehicles. The complaint pattern described soft pedal feel or intermittent pedal-to-floor events, conditions that can extend stopping distance and increase crash risk.
Honda’s root-cause analysis identified residual plasticizer in the brake reservoir hose as the contamination pathway. The plasticizer leached into the brake fluid and was absorbed by the master cylinder’s secondary cup seal, causing it to swell. Radiant engine heat during operation expanded the swollen seal further, allowing brake fluid to bypass the seal at the master cylinder during slow brake-pedal applications.
How the Recall Scope Compares to the Probe
The investigation focused on 2019–2020 model-year vehicles. Honda’s Recall 25V859 expanded that range substantially, covering all 2016–2020 model-year Acura ILX units produced between October 9, 2014 and January 29, 2020 — a total of 70,658 vehicles. The broader scope reflects the manufacturing-records basis Honda used to identify all potentially exposed units, even where the estimated percentage with the defect is small.
Remedy
Dealers will replace the brake master cylinder with a redesigned component featuring inner cup seals made of a different material, intended to provide improved sealing capability and prevent the fluid-bypass condition. The Acura ILX has not been in production since 2022, but the recall remains active for owners of affected vehicles.
What Happens Next
With Honda’s recall in progress, ODI closed PE25015 without further enforcement action. The closing resume notes that NHTSA reserves the right to take additional action if future circumstances warrant — standard language that preserves the agency’s option to reopen the matter if new failure data, complaints, or warranty patterns emerge.
The closure follows a pattern seen in other recent brake-defect probes, including the Ford E-Series hydraulic line query NHTSA closed earlier this month, in which the agency accepted manufacturer remedy data and ended the investigation without further action while preserving reopening rights. The Acura ILX matter was previously covered by The BRAKE Report when Honda filed the underlying recall.
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