Instability/wandering steering on freeway/highway speeds

During the long highway drive home after I picked up the new 2020, I also noticed the steering needing frequent inputs to keep straight. One thing that made it better for me was switching off Lane Departure Warning, which seemed to make the steering heavier and easier to control to keep straight. So, either I am prone to always overcorrecting the steering (if the steering is lighter, which seems to be the case with Lane Departure Warning on) or there's some kind of issue noted in the above posts.

EDIT: I had the tire pressures set to 38F/37R before I left the dealership.

 

Not sure if this has been mentioned, but tires out of road-force balance also could be a cause. Road Force Balancing helped fix the wander issue on my Camry Hybrid.

 

Just wanted to add. I have Prius Prime and Corolla. This floaty feel is real and probably not the same issue as with a Camry which doesn’t commonly have this issue.

for me it’s mostly crosswinds on highway- on my daily drive I experience this always on a bridge on garden state parkway. When I lived in Midwest cross winds were strong and also experienced this.

i complained to the dealer and they did alignment which made significant improvement with my Corolla. It’s slightly less on Prius but I will ask next time for alignment.

if it gets worse ask for alignment- if bearable maybe ok to live with but I personally hate this feature of the Prius and Corolla

 

I had the same experience, 2017 Prius Prime. The culprit is the lane assist feature. In order to ensure that you are paying attention it requires constant steering input. This is how it senses that you have taken your hands off the wheel. It's not terribly hard to get used to, but by the same token, it would be nice if they used another method that was not quite as intrusive to the driver's enjoyment of the drive.

I responded to this old thread because it was bumped up AND there was only the one response that was, in my opinion, completely correct.

 

You have to reset steering similar to this. This video is for a 3rd gen Prius though so you'll have to find the way for 4th gen.

 

George - in video above ^ is the macgyver of car fixes turned into DIY at home without expensive equipment needed. When ever he finds one he posts a youtube on it.
Not always the kind of fix an owner would want to do to a newer vehicle, but for older cars especially his DIY's can save big time - $ - and frustrations, when they are as simple as the procedures shown in the videos.

the vehics411 youtube channel is another good one, when it fits the issue the car has.
VEHIX411 - YouTube

 

That video doesn't seem very useful. It shows a paperclip between pins 4 and 13 (CG and Tc), which is the normal pair of pins you use for retrieving trouble codes. In fact, his video shows the dash lights all blinking, but he doesn't even bother reading the codes they are blinking out. Big missed opportunity there to find out what issue the car was really reporting.

Edit: counting the blinks in his video, he has 33 on the ABS light (C0210, rear right-hand wheel speed sensor circuit), and 36 on the ((!)) light (which means "go look at the ABS code"). I couldn't count the VSC light blinks because he didn't keep that light in the frame. That's too bad, because the VSC light is where any codes about the steering angle would be.

He seems to think he is resetting a steering sensor with that procedure. But that reset procedure uses a different pair of pins (CG and Ts, 4 and 12), and you don't just jumper them together once and sit there. More details on that procedure are in this post.

Here's a little from that post, just outlining how the steering angle sensing works:

That post also describes a handy "SENSOR CHECK USING THE TEST MODE" procedure that's in the repair manual, that lets you drive a certain predetermined pattern (you kind of need a biggish empty parking lot) while the ECU checks all of the acceleration, yaw, steering angle, master cylinder pressure, and wheel speed sensors, and if it beeps for 3 seconds at the end of the sequence, you know everything checked out.

 

I have used this method on my 3rd gen and it effectively improved steering, handling, wandering, and even braking. Its like a re-calibration of some sort.

 

I am glad to hear about your improved steering, handling, wandering, and braking.

We might be able to learn something for the community if we could get more information on what improved and why.

We already do know what the Tc to CG jumper procedure does, and what the Ts to CG jumper procedures do; they are documented in the manual, and numerous PriusChat posts confirm them doing just what the manual says they do.