1. Attachments are working again! Check out this thread for more details and to report any other bugs.

HELP PLZ! What happens if you accidentally drive in B mode for any distance?

Discussion in 'Gen 2 Prius Technical Discussion' started by MMBH, Jun 11, 2018.

  1. MMBH

    MMBH Member

    Joined:
    Apr 12, 2018
    155
    43
    0
    Location:
    USA
    Vehicle:
    2017 Prius Prime
    Model:
    Premium
    I gave my 2004 Gen 2 Prius with 225,000 miles to my nephew. Well his brother borrowed it for the day and apparently drove it around in B mode!!! :( Now it loses power going up hill but then you turn it off and back on and it seems to work OK again. Please advise. TY!
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    108,639
    49,359
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    nothing. maybe lower mpg's. of course, anything can affect an old car.
     
    McMasterc likes this.
  3. Raytheeagle

    Raytheeagle Senior Member

    Joined:
    Jul 1, 2016
    11,251
    15,481
    0
    Location:
    Bay Area, California
    Vehicle:
    2019 Prius Prime
    Model:
    Prime Plus
    I believe another feature that doesn’t work is cruise control, but that’s while in B mode;).

    Should be no lingering effects:).

    Good luck and keep us posted (y).
     
  4. MMBH

    MMBH Member

    Joined:
    Apr 12, 2018
    155
    43
    0
    Location:
    USA
    Vehicle:
    2017 Prius Prime
    Model:
    Premium
    Thanks, so, while I have your attention, another question I have is that there are a lot of dummy lights on the dash that have been on for a while, even before I gave the vehicle to my nephews, but we just covered them up with electrical tape. Is this common in the old gen 2's? And if so, is there any easy fix? Is it some sort of module that needs to be replaced? And if so, how pricy will it be? TIA!
     
  5. Raytheeagle

    Raytheeagle Senior Member

    Joined:
    Jul 1, 2016
    11,251
    15,481
    0
    Location:
    Bay Area, California
    Vehicle:
    2019 Prius Prime
    Model:
    Prime Plus
    All of the lights on the dash have a meaning;).

    The challenge is figuring out what they mean. Think of it as a game where the goal is to have none of them displayed :).

    No cheating by applying the electrical tape :cool:.

    Where in the greater US of A are you located?

    Definitely worth researching the codes (y).
     
    SFO, Tyfly and PAUL SCHULTZ like this.
  6. PAUL SCHULTZ

    PAUL SCHULTZ Member

    Joined:
    Feb 5, 2018
    103
    66
    0
    Location:
    Michigan
    Vehicle:
    2008 Prius
    Model:
    Touring
    What lights exactly? Are you sure they are not working properly? If working as designed have you explored what system they are giving you a warning for? I've never been a fan of covering with tape. If it is your display then there are threads on repairs but I believe the symptom for defective display is that it blacks out.

    Paul

    Edit: Ray beat me to it!
     
    Raytheeagle likes this.
  7. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    108,639
    49,359
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    dash lights mean the are trouble codes. a dealer can read them, or you can buy a proper code reader. it would be a good idea to find out what they mean, and follow up on anything important.
     
    Raytheeagle likes this.
  8. MMBH

    MMBH Member

    Joined:
    Apr 12, 2018
    155
    43
    0
    Location:
    USA
    Vehicle:
    2017 Prius Prime
    Model:
    Premium
    I've been to the mechanic about it. He said it wasn't anything to worry about. He is a highly regarded automotive shop so I trust his judgement. I don't recall which ones were on constantly and which ones were intermittant. I'll either have to ask the mechanic or the next time my nephew stops over I'll take the tape off and take a picture of them. It was an issue at night with them reflecting on the front windshield. Hence the tape. I was just wondering if it could be a short and if that combo meter thing might be an option to resolve this sort of issue.
     
  9. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    108,639
    49,359
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    no, it just goes blank. how is the 12v health?
     
  10. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    108,639
    49,359
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    i would certainly like to know which dash lights are insignificant, for future reference, thanks!
     
    SFO and Raytheeagle like this.
  11. MMBH

    MMBH Member

    Joined:
    Apr 12, 2018
    155
    43
    0
    Location:
    USA
    Vehicle:
    2017 Prius Prime
    Model:
    Premium
    ;) I was concerned initially, but honestly it's been like that for the past few years now at this point and so I'm guessing that they aren't really serious and that it's some sort of short effect.
     
  12. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    7,627
    3,848
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    The problem with the "ignore strategy" is that if there are new serious codes that come up since you last scanned the codes, you will never know about it unless you adopt a regular scan strategy.

    Warning lights generally are not something to ignore. Even if they redeemed not too serious, the problem they represent still should be fixed. If they are not too serious, shouldn't cost too much.
     
    Raytheeagle likes this.
  13. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    55,396
    38,636
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    B mode reduces the hybrid battery charging rate; maybe sustained B mode would be drawing the state of charge down. But I think it'd spring back with switching to D.
     
  14. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,286
    10,140
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I was thinking the opposite -- B should tend to increase the battery charge a bit, but at the cost of extra (and needless) fuel consumption.
    Agreed here -- unless there is something important hidden by those taped-over dashboard lights.
    That should be unrelated to B mode, present or past.
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    55,396
    38,636
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    I see your opposite and raise you, an opposite. I'm not sure though. I do know it's popular lore to use B on long downhill stretches, to delay fully charging, since it tends to do engine braking. But I seem to recall in any sort of driving it reduces charging. I'm by no means sure though.
     
  16. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    7,627
    3,848
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    No, Mendel is correct.

    The point of "B" is to reduce input into the HV battery and substitute the reduced re-gen with higher engine braking. It is specifically for descending long (e. g, mountain passes) descents.
     
  17. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,286
    10,140
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I agree on the downhill, as some gravitational descent energy is diverted to engine braking instead of the battery or brake pads and disks.

    But on flats, it seems to lead to more aggressive regeneration drag than does D-mode, and only part of this is extra diverted to the engine. The rest goes into the battery. Plus, it prevents ICE auto-shutoff when gliding and when stopped, wasting some gasoline. That extra time spinning the ICE also continues charging the battery at a slow rate.
    The point of "B" is really to reduce heating of the friction brakes when the HV battery gets filled and can accept no more. But it works best when B is engaged at the top of the hill, delaying the filling of the HV battery and reducing the amount of time that the ICE spends screaming like a banshee.
     
    #17 fuzzy1, Jun 12, 2018
    Last edited: Jun 12, 2018
  18. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    7,627
    3,848
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    You are also correct and I can see how you might have misunderstood my post, but I took it as a given that the result would be reduced use of the brakes, but I shouldn't have assumed everyone would be on the same page.

    So perhaps I should have phrased it thus; The point of "B" is to reduce heating of the friction brakes and it does this by reducing input into the HV battery and substituting the reduced re-gen with higher engine braking. And it works best when B is engaged at the top of the hill.
    I think you'll find the more aggressive braking feel is the substitution of a more aggressive engine braking configuration – at the expense of re-gen. I am happy to be wrong about this, if you have any quantitive data to show my understanding is not right. Always wanting to learn.
     
  19. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,286
    10,140
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I'll agree with you on two major cases that don't apply to the OP's situation, dispute one corner case that also doesn't apply here, and leave the OP's situation as unresolved.

    The agreements: on major downhills, compared to foot braking or retarding cruise control, B mode does use heavy engine braking that doesn't leave as much current available for battery charging.

    The disagreement corner case: on mild downhills when moving slowly (under 25 mph??), if B is engaged while the ICE is stopped, braking effect is increased even when the ICE doesn't spin up. In such cases, the battery charging current is clearly increased.

    But the OP's situation concerns B-mode vs simple ordinary D-mode driving without significant hill descents. I.e. without extended foot braking or cruise control drag, likely little or no heavy engine braking, so the above scenarios generally don't apply. Uphill, B is a generally a No-Op. Highway cruising with propulsion applied, it is again generally a No-Op. The relevant scenarios are thus common flat-land stop-and-go city driving, plus possibly the gliding phases of cases of highway driving with the (aggravating for some of us passengers) thermostat-style gas pedal control (On-Off-On-Off...). These are cases that involve mild engine braking, plus times when B-mode prevents ICE auto-shutoff.

    I don't have battery charge rate X-Gauge programmed into my ScanGauge-II, so lack quantitative evidence either way. So I'm going with my seat-of-the pants feel until something more definitive appears.
     
    #19 fuzzy1, Jun 12, 2018
    Last edited: Jun 12, 2018
  20. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    55,396
    38,636
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    One reason we're all milling around: the Owner's Manual doesn't really explain B mode. I've heard it's there in part because it's mandatory to have some "low gear"?
     
    fuzzy1 likes this.