Hazard (fishtailing risk): In rain with LTA ON, small but critical driver steering corrections near center are overridden by EPS/LTA, which apply centering torque into steering dual compliance creating a real steering wheel deadband canceling the driver’s turning of the wheel across the deadband; then the steered wheels snap abruptly to the steering wheel position. The significantly delayed response and snap overcorrection, caused cause fishtailing (causing a miss with a car, then a semi), just like the car suddenly had loose ball joints. Conditions: 40–50 mph, intermittent heavy rain, wipers high, spray, occasional false lane detections. Dealer response: Acknowledged the general behaviour. Refused diagnostics; advised turning LTA OFF or lowering sensitivity. Reference: Technical appendix in Toyota.txt (mechanism, thresholds, dual‑compliance explanation, SAE 2019‑01‑1516). SAE Technical Paper 2019-01-1516 (Fu et al., "Control Strategy to Reduce Torque Oscillation of the Electric Power Steering System") Observer credentials: Retired 39-year integrated circuit design engineer; 23 US patents (8 involving nonlinear feedback/deadband control).
NHTSA ODI 11700388