Prius (2010-12) :: Power Steering Wheel Shaking While Driving At Highways Speeds

I bought a new 2010 (Gen III) Prius IV one week ago. I have driven it less than 200 miles. Last night, I experienced a few seconds of steering wheel shaking while driving at highways speeds. I assumed I had hit uneven pavement. At no point was it difficult to turn the wheel. But after the shaking, the car seemed to sometimes drift to one or the other edge of the lane. I chalked that up to unfamiliarity with the car and to rain and darkness. Today, I read Forum posts that described the lighter touch that usually works and the importance of wheel alignment.

After the shaking, another 45 minutes of driving, and a half hour parked, I headed home on a slower road. That is when my wife noticed that the Electric Power Steering warning light was on. We are both pretty sure it was off before that. This morning, I pulled out of the garage and back in, and turned the wheel both ways as it moved. The light did not come on.

I called the dealer to discuss what had occurred. I made a service appointment for Monday so they can check it out. Someone in a Gen II forum (where I mistakenly posted this at first) advised me to pull over and take an evidence photo of the light if it comes on again.

The PS warning light wouldn't be too surprising to see in a Prius driven tens of thousands of miles. If yours ever came on when your Prius had low mileage, I'd be curious to know the outcome. I misidentified a benign icon as the EPS warning light.

The mechanic became suspicious when he couldn't find any code or any trouble. We sketched the icon we remembered seeing for the service supervisor. He explained that it was the cruise control light. I either forgot I had turned cc on or I had pushed it accidentally when I operated the wipers.