Hill Start Assist & Shifter Problem

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by JimN, Jan 19, 2010.

  1. JimN

    JimN Let the games begin!

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    I tend to have a heavy foot on the brake when stopped which activaes the Hill Start Assist.

    This morning during my normal commute I notice the HSA doesn't engage every time the brake pedal is pushed to the floor, perahps 1/3 to 1/2 the time it doesn't engage.

    At 8:00 the car is parked in Ready mode with the doors locked manually and the fob in my pocket. Everything appears normal until I fully depress the brake & try to shift into reverse. The shift knob won't move as if locked in place. B, D, R, N makes no difference.

    Over the next 30 minutes or so I try powering down & restarting several times. Again, everything looks normal. No extra idiot lights or unusual beeps. After about the fifth or sixth time the brake pedal acts differently. First, spongy as if there wasn't any brake fluid and it goes to floor very easily. I let up on the pedal and the next stroke is very hard like applying power brakes without power and with some resistance to the shift knob I get into Reverse. I back out of the space and can drive normally and have standard braking ability. I call Cherry Hill Toyota to tell them I'm on my way in.

    Over the 35+ mile ride the car handles like nothing happened. Most of the times stopped at traffic lights the HSA engages. Some times it did not. Once in Burlington City and most notably at the 2 traffic lights just before the dealer and again on their lot in front of the garage door.

    My ScanGauge II did not find any codes. OAT was high 30's F, about what we experienced the last few weeks, and it was foggy.

    After having the car for ~ an hour I go on a test drive with the Tech so he can demonstrate that nothing is wrong. (During the ride the car performed normally.) I asked if he pulled any codes from the Brake ECU. His reply was there are 23 computers in the car and there weren't any codes in any of them. He said he'd contact Toyota & do some research as he hasn't heard of this situation before.

    Any insight is greatly appreciated & will be shared with the dealer as I want to resolve this ASAP. Getting stuck by the office on a workday is one thing. Getting stuck elsewhere could be worse.

    I put 1000-1100 miles on the car since I bought it a month ago.

    Thanks for your help.

    Jim.
     
  2. Bobsprius

    Bobsprius BobPrius

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    Jim,

    May I really suggest "lighter brake pedal application". I have a V as well and have yet ot engage the hill start assist. In fact I wondered one day if mine even worked! :) Why not try starting the car and letting it run slightly before backing and see if that fixes it too. Maybe you didn't get enough pressure when the brake actuator kicked in? What's odd is that you couldn't duplicate it at the dealership. It may be some commonality your poerforming or sequence. (I am beginning to think that for some issues I have seen, only since I have not, and several of us have the V). Not passing any blame here, just trying to see what things may be common that one does and the other one doesn't that would present itself with your scenario.

    I think after reading your last story about the safety connect, you answered my question, on what happened. Just try to be lighter on the brake and you should be good...

    You get the indicator so you know when you engage it, and it only lasts a short time. I don't have the manual here at the moment but there was some auto feature whereby if you didn't do something in x seconds it would disengage...

    But try the light foot approach and see if it helps.;)
     
  3. JimN

    JimN Let the games begin!

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    Understood & no offense taken. I know why one has to ask: Is it plugged in? Is it turned on?

    I would be thrilled to death if this is just an ID10T problem and would leave it at that if this was the 1st day or trip. I'm not claiming to be a G3 expert but it seems that if this is just "technique" it should have happened sooner. "Brake firmly engaged" is a tough habit to break overnight.

    Unfamiliarity with the car was an issue on "day 0". Not knowing about HSA during the test drive I remarked about the VSC icon while at a dead stop. Salesman couldn't explain it. Another explanation was that some very small amount of wheel slippage was detected which tripped the light. My reply was, "NOT at a dead stop. If wheel slippage is detected then something's wrong." I realized it was the HSA reading the 2010 "problem" thread.

    (Cherry Hill Toyota is owned by Holman which owns many dealerships. Three of them are/were Saturn lots. I got the impression that the displaced Saturn employees transferred to the Toyota lot.)
     
  4. Tom183

    Tom183 New Member

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    Did the tech check the fluids and pressures (and sensors) in the braking system, or did he just go for a ride?
     
  5. adrianblack

    adrianblack Member

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    So you come to a stop and then keep applying heavy pressure and the pedal goes to the floor or does it seem to be limp under your foot and go to the floor after a little while on its own? If the car has power and there are no faults detected, the pedal is only acting on a brake stroke simulator and not the actual brakes (since those are operated by the computer) so there should be no change in pedal feel no matter what happens. From what I can tell the stroke simulator uses brake fluid to simulate the feel of a brake pedal, so maybe there was a bubble in the system changing the feel momentarily. This wouldn't throw an error code as the sensors and system was all working normally -- just the feel was odd with the simulator.

    On my car to activate HSA, I push the pedal to the floor and you feel a click as it activates it. It's so far down on the stroke I can't imagine activating it by mistake.... Also, while the Prius is stopped, it's not trying to move the car forward (against the brakes) unless you are almost completely off the brake pedal... I love that as my last car (a manual transmission car) required almost no pressure to keep the car stopped at a light, so I'm used to barely applying the brakes at a stop.

    What I am really surprised about is the shifter. The shifter is purely electronic like a joystick and has no lockout mechanism that could prevent movement. Could it be that something got wedged in under the gap where the shifter moves around? When you finally pushed hard enough it selected reverse and the obstruction fell inside the unit? Too bad the dealer didn't come get the car before you were able to move the shifter so they could have seen it first hand.
     
  6. JimN

    JimN Let the games begin!

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    I'm the only driver so if something fell into the shifter it would have happened in the first 100+ miles while in the dealer's inventory. He did ask if anything went down the shifter. At this point I don't believe I want an exploratory just to see what's in there. If the thing fell into an empty space where it won't cause anymore problems is that good enough for me?

    "So you come to a stop and then keep applying heavy pressure and the pedal goes to the floor or does it seem to be limp under your foot and go to the floor after a little while on its own?"

    The "limp" & "stiff" pedal happened only once--when stuck in the lot just before I was able to shift. As I recall, the pedal went limp. I released the pedal and the next stroke was "stiff". I'm not sure I even pushed the pedal all the way to the floor. Normal feel after that. I don't ever remember hearing or feeling a click when HSA engages. I will pay more attention tomorrow.

    When the brakes were lightly applied (just holding the car stopped) the Gen2 drew current from the traction battery which didn't happen when the pedal was pressed harder.

    "Did the tech check the fluids and pressures (and sensors) in the braking system?" Apparantly he did not as it is not noted in the on-line service record. Since I have his e-mail address I'll ask.

    Here's the latest update from the Shop Foreman:

    "I called my engineer group in regards the shifter issue in your Prius. They have no issues where the shifter would not move.
    I mentioned about the Scan Gauge that you have installed, they stated it could possibly be a problem but not likely.
    They asked to have you monitor the issue as to temperature, brake on or off, ready light, check engine light and or triangle with exclamation point.
    Please keep me informed."
     
  7. GreenClipper

    GreenClipper Senior Member

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    Ok, did I miss something in the manual?? Do all the GenIII's have the HSA, (I assume that is the "Hill Start A----?). Are you suppose to push the brake pedal "all the way to the floor"? Is that SOP for ingaging the HSA, if we all have it? On conventional cars I've owned if the brake pedal went all the way to the floor you were in trouble!
     
  8. adrianblack

    adrianblack Member

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    I noticed that Gen II behavior where it sucks up power when stopped. That doesn't happen on the Gen III. (You can use my AMP gauge to see battery draw or MG1/2 torque values. They all sit at zero until you are almost completely off the brake....)

    I had a rental Gen II and when I first got my Gen III I was pushing the brake pedal hard to make sure no power was being wasted... But now I know no power is going away, I am back to my light pressure to keep the car stopped.

    And I'm with you -- don't bother opening up the shifter. Whatever it was is inside it now and shouldn't cause a problem.
     
  9. JimN

    JimN Let the games begin!

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    Yes, HSA is Hill Start Assist and the pedal has to be pushed almost to the floor to engage. It is standard so every II-V has it.
     
  10. JimN

    JimN Let the games begin!

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    Thanks for the info & reassurance. I'll try to lighten up.
     
  11. tumbleweed

    tumbleweed Senior Member

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    Jim, after a little thought about your problem I tend to agree with Adrian, if the shift lever itself wouldn't move something must have been blocking it. Which would mean either something fell down in and got stuck or something mechanically broke and part of it got in the way or something like that. Whatever it is will still be down in there somewhere, I think I would want to find out what it was.

    I will check my brakes and HSA today and see if I can duplicate what you felt.

    The brake/HSA and the shifter problem may be unrelated issues.

    Edit: HSA works pretty much as you described, brake pedal needs to be pushed almost clear down to activate. Tried it several times, worked fine each time. Brake pedal can be pushed clear to the stop and feels pretty much the same in Ready or when the car is off. Not exactly squishy but not firm the way normal braking system acts. With the car off the pump still runs to charge the accumulator so I think it should feel the same way.
     
  12. JimN

    JimN Let the games begin!

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    I was told the brake fluid, pressure & sensors were not checked as they would have thrown a code.

    I needed to secure the slack in my ScanGauge cable so while I was down there with the car OFF I played around with the brake. Travel felt "normal" and I did hear it pump once about every stroke.
     
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