During a controlled low-speed autocross event (~55 mph entry), I applied the brake pedal firmly to decelerate for an upcoming turn. The vehicle failed to decelerate at anywhere near its rated capability. Despite full, sustained pedal application, the car would not slow adequately, departed the course, and struck a barrier, resul…
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During a controlled low-speed autocross event (~55 mph entry), I applied the brake pedal firmly to decelerate for an upcoming turn. The vehicle failed to decelerate at anywhere near its rated capability. Despite full, sustained pedal application, the car would not slow adequately, departed the course, and struck a barrier, resulting in a total loss. No injuries occurred. This happened on smooth, dry pavement where 100+ other vehicles braked normally. The failed system appears to be the electronic brake control (ABS/VSA) and/or its input signaling. Event Data Recorder (EDR) data was professionally extracted and shows: accelerator at 0% for ~3.5 seconds before impact (ruling out pedal misapplication); ABS logged ACTIVE while stability control was "not engaged"; and peak deceleration of only ~0.67 g with a momentary 0.00 g dropout, versus this model's documented ~0.9–1.0 g capability. Notably, the service-brake switch intermittently read OFF while ABS was simultaneously active — a signal inconsistency, since ABS modulates driver-applied pressure. This indicates a possible brake-switch/signal-integrity or ABS/VSA control anomaly that reduced or withheld commanded braking. Safety risk: complete loss of expected stopping power at speed. Had this occurred on a public road with a pedestrian, crossing traffic, or a stopped vehicle ahead, it could have caused serious injury or death. The vehicle was under the 3-year/36,000-mile warranty with a stock, unmodified brake system. Prior symptom: on the immediately preceding run, dashcam footage shows an abnormal brake hop/oscillation, which may have been an early sign of the same fault. The vehicle, EDR data, and synchronized dashcam footage are preserved and available for inspection. The manufacturer extracted the EDR but has not yet performed a root-cause teardown. No dealer, police, or insurance inspection has occurred. Root cause: UNKNOWN pending modulator interrogation.
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