Slip indicator light when braking

I have over 6K miles on my 2017 and I have not seen this issue.

 

By any chance Is this happening on smooth metal covers or plates, or is it on asphalt / tar / concrete? Loss of traction on smooth metal has been known to do this on previous cars.

Is it happening on smooth roads, or on rough surfaces, broken pavement, bumps, or potholes? In previous generations, hitting bumps or potholes has been known to trigger ABS and cancel regeneration, but with a momentary delay that creates a disconcerting 'surge' feeling. This fits with your gentle braking scenario, but is not consistent with the jerkiness or rear end feelings you mention.

I've experience rear end jerkiness on a previous car when a brake shoe wore down and suddenly hit the rivets. But that is not consistent with your rear disc brakes or young car.

 

I was real big thing in my gen 2. The Gen 4 is much better. It is a wheel not going the same speed as the other wheels. Caused by hitting a bump while braking

 

I noticed it a few times earlier on but only with fairly hard braking, mostly on wet roads, and I assumed it was a "too anxious" ABS kicking in, and tyres which are ECO, not "MaxGrip". Never noticed the light though.

 

Have you driven these roads in Prius specifically?

Prius needs to have both front wheels getting smooth traction in order use regenerative braking. This is 2-wheel-only braking. If either one slips or is momentarily in the air (over a pothole or just past the crest of a bump), the car cannot brake properly, so must cancel regen mode and transition to 4-wheel friction-only braking. Often, this mode transition is not instantaneous or seamless, so the driver can feel it. On the 2010s and early 2011s, the pause was disconcerting enough to force a recall, which reduced but did not eliminate it.

Lacking regeneration, non-hybrids don't have this mode transition. They are already in 4-wheel friction braking from the very start. Each wheel is independently controlled by the ABS, so loss of traction at a single wheel doesn't pause braking at the other 3.

When you feel it again, please get back to us with more description of the particular road conditions.

I don't recall seeing any comments about Gen4 being more sensitive than previous years, but the installed base isn't all that large yet.

 

With the Gen 3, the Plus (v wagon) and the Gen 4, I've had it happen over manhole covers and potholes filled with loose gravel, it only happens on gentle (regen) braking as the friction brakes take over on harder braking.

 

Excellent explanation of somewhat troubling behavior I noticed in my Gen2. I knew it was sometimes discomfiting but couldn't figure out why or what exactly was happening. Thanks for this!

 

Do be aware that this will vary considerably among various hybrid and EV models. E.g. the first edition of the Ford Fusion Hybrid was noted as having a more seamless transition than the 2010 Prius (before the recall, I didn't see any comparison after). And different models have very different maximum regeneration levels, so their braking transition points will be quite different.

 

FWIW, I used to get the same thing on my CR-V petrol auto, but haven't not noticed it yet in my Prius.