NHTSA Complaint #11045188 — 2005 TOYOTA SIENNA

TWO INSTANCES IN OCT 2017 OF BRAKES ACTIVATING WITHOUT DRIVER ACTION. BRAKING ACCOMPANIED BY BEEPING - POSSIBLY ELECTRONIC STABILITY CONTROL (ESC) ACTIVATION SIGNAL. BRAKING REDUCED SPEED APPROXIMATELY 10-15MPH. BOTH INSTANCES OCCURRED ON THE SAME ROAD, A CURVY 45MPH LIMIT ASPHALT 2-LANE. CONDITIONS DRY, ~50 DEG F. BRAKING OCCURRED ON A STRAIGHT SECTION AND DID NOT PULL THE CAR TO ONE SIDE. DO NOT BELIEVE ANTI-LOCK ENGAGED. VAN HAS 137K MILES.TOYOTA SERVICE (11/9/17) : "NO PROBLEMS FOUND NO CODES STORED NO VEHICLE EVENT LOG (VEHICLE DOES NOT HAVE THAT CAPABILITY) MORE OBVIOUS AND LIKELY CAUSE COULD HAVE BEEN THE FACT THAT THE FRONT TIRES WERE AT 20 PSI AND THE REAR AT 35 PSI, THE DISPARITY IN WHEEL SPEED SIGNALS COULD HAVE TRIGGERED A FALSE EVENT." VERBAL REPORT CONFIRMED "NO PROBLEMS FOUND" INCLUDING STEERING RACK BUSHINGS, STEERING ANGLE SENSOR, AND WHEEL SPEED SENSORS. THE SERVICE REPRESENTATIVE, WITH 6 YEARS EXPERIENCE AS A MECHANIC, SAID HE HAD ENCOUNTERED THIS PROBLEM BEFORE BUT IT WAS RARE. HE ALSO STATED THAT AN APPARENT DIFFERENCE OF ONLY 1MPH IN WHEEL SPEED COULD BE ENOUGH TO CAUSE INADVERTENT ESC ACTIVATION. HOWEVER, HE WAS UNSURE WHY THE PROBLEM, IF IT WAS CAUSED BY THE FORE/AFT INFLATION DIFFERENCE, WAS SO INTERMITTENT. THE DEALER WAIVED THE $98 DIAGNOSTIC FEE. A DRIVE ON THE SAME ROAD ON 11/10/17 DID NOT PRODUCE THE UNEXPECTED BRAKING, BUT IT IS UNCLEAR WHETHER THIS MEANS THE EQUAL TIRE INFLATION FIXED THE PROBLEM AS, AS STATED, THE PROBLEM WAS INTERMITTENT. SYSTEMS DESIGNED TO IMPROVE SAFETY SHOULD FAIL IN WAYS THAT DO NOT COMPROMISE DRIVER CONTROL AND OWNERS SHOULD BE MADE AWARE OF CRITICAL MAINTENANCE PROCEDURES TO AVOID SUCH FAILURES. FAILURE OF ACTIVE SAFETY SYSTEMS SUCH AS ESC, RISKS DELAYING ACCEPTANCE OF INCREASING LEVELS OF DRIVER ASSISTANCE INCLUDING FULL AUTONOMOUS CONTROL, AN ADVANCE THAT PROMISES DRAMATIC REDUCTION IN ROAD MORTALITY.