Jerking motion going downhill (MAX equipped)

[jimr]

I've encountered a very noticeable and bothersome jerking motion going downhill when the traction battery is fully charged, and shift lever is in "S" to help reduce speed. The attached pic shows the options I've enabled which helped diagnose the problem. The traction battery status (LHS panel 8 bars under blue "MAX") needs to be full to reproduce the problem. When it happens the instantaneous MPG (RHS white bar above "Total Average" though it's zero in the pic because I was stopped) bounces rapidly between around 30 MPG and 60, seemingly causing the jerking motion by intermittently applying unwanted power.

It seems if either 1) traction battery status is less than full, or 2) shift lever is in "D", the problem doesn't occur. Possibly in "D" it occurs, but much less pronounced. Anyone else encounter this issue, or know how to report it to Toyota?

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[Dead Horse]

S is the manual shift mode isn't it? Which means that it's going to stay in the gear you put it in (unless the computer determines that you're going to hurt it, in which case it's going to stop listening to your inputs). If that's a lower gear than normal for that speed in regular driving, it's going to be jerky with even light throttle inputs.

Or your truck is busted

 

[jimr]

S is the manual shift mode isn't it? Which means that it's going to stay in the gear you put it in (unless the computer determines that you're going to hurt it, in which case it's going to stop listening to your inputs). If that's a lower gear than normal for that speed in regular driving, it's going to be jerky with even light throttle inputs.

To clarify, the problem is when going downhill and not applying ANY throttle inputs. What appears to be happening is the car itself is applying unwanted throttle inputs, rapidly on and off, thus the unwanted jerky behavior. The shift lever is in "S" to set a max gear, not a fixed gear. I generally set it to increase the rpms for braking but never over 3000. Nothing major. Not sure why traction battery needs to be full for this to happen, which is a real mystery. I'm vainly hoping it's a software issue that can be fixed, but I'm doubtful.

Note also I live in mountainous terrain, so anyone driving in relatively flat country probably won't notice this issue.

 

[AZTrail]

Might be related to the 4Runner not wanting to overcharge the traction battery. Going downhill with no throttle input creates a lot of regeneration energy. If the battery is already fully charged the 4Runner may be trying to do something to prevent charging the battery more

 

[jimr]

Might be related to the 4Runner not wanting to overcharge the traction battery. Going downhill with no throttle input creates a lot of regeneration energy. If the battery is already fully charged the 4Runner may be trying to do something to prevent charging the battery more

Yes this theory makes sense. That's kind of why I was hoping there might be (or Toyota can come up with) a software fix that says effectively: "Traction battery is full. Disable regenerative braking completely until it's only 80% full". If what you says is correct, it's behaving like the threshold is set at 99.9%, causing the jerky behavior.

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