Steering Power Low

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Priyzf, Oct 16, 2018.

  1. Priyzf

    Priyzf Junior Member

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    Driving on the highway at 70mph the Prius suddenly turns off. I coast to the side, waiting 2 hours for a tow truck. Steering Power Low is the message I got. I replaced the 12v battery the next day which fixed the problem. Total cost $400 including the tow and battery from dealer
     
  2. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    good you were able to navigate from the traffic without power. Did you think to get stored emergency codes while at the dealer?
     
  3. The Professor

    The Professor Senior Member

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    I'd be surprised if that was the problem. A 2 year old 12V battery should be fine, especially in a Prius were it isn't used for much at all. I would expect to get 5 years without serious problems, but maybe replace after 3 at earliest.

    But more importantly, when in Ready mode (i.e. driving) the 12V battery isn't even being used; all 12V power comes from the DC-DC converter which converts power from the high voltage traction battery into around 12V to power everything electrical (apart from the motor and air con, which are powered directly from the high voltage traction battery). Power would only be drawn from the 12V battery in Ready mode if the maximum current of the DC-DC converter was exceeded. If I remember correctly it's rated at 100 amps, and the maximum draw from the car with everything on (heated seats, fan, heated rear window, headlights, 12V battery charger, etc) is around 80 amps. In fact, the 12V battery is being charged, not emptied, while in Ready mode, so even if it wasn't present it still wouldn't cause the issue here.

    I would suspect a loose connection (that replacing the 12V battery may have fixed), or a bad DC-DC converter or cooling issue thereof.

    Someone else with more technical knowledge than I might have a better answer, but I just can't see the 12V battery being the cause.

    The error message can come up if there is an electrical power issue (low voltage, or off) as the power steering is electrically powered.
     
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  4. fuzzy1

    fuzzy1 Senior Member

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    This is the same message Bob Wilson received when (intentionally) running his Gen3 out of gas. It continued driving until out of HV battery too, then he received this as the first warning, as the 12V supply began to fail:
    [WARNING] Running out of gas (Gen III) | PriusChat

    If you weren't out of fuel, then I'd be concerned about a 12V charging system failure.
    Or it could be like my dad's ATV a couple months ago. Charging system failure, but simply replacing the 12V battery produced enough voltage to turn out off the warning light. He thought it was fixed, but I warned him that it was only temporary, until the battery ran down again. (He is in poor health with very low mobility, so it could strand him well away from the house.)

    So if you (OP) have a voltmeter available, make sure the 12V system is running at least 13.5V while the car is READY. If it is in the low-mid 12s, then the charging system has failed (or a loose connection), and you'll have another failure when the little battery drains out.
     
  5. Priyzf

    Priyzf Junior Member

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    I didn’t pull any codes while at the dealer. The Low Fuel light was on, but after I pulled over, the ICE fired up for 10 seconds then cut off with a Steering Power Low message. After reading Mr. Wilson’s post on running out of gas, this may of been the cause. I’ll never know because after I installed the new battery, I put 2 gallons of gas in it for good measure.


    I drove maybe 75 miles after the Low Fuel light came on. I’ve done that many times before, but maybe this time it caught up to me as I had the wife, baby, and I live in the Bay Area with plenty of mountains to climb.


    On a side note, I couldn’t get the Prius in to neutral after it was on the flatbed because the 12V battery was too low. We had to push/slide it off the tow truck. I’m hoping I didn’t damage the drivetrain. Only time will tell. Thanks for the replies
     
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  6. The Professor

    The Professor Senior Member

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    Yep, 75 miles is about the upper limit for the low fuel light, assuming the drive is economical (not carrying lots of passengers, or driving hilly terrain). One video I saw the Prius ran out after 50 miles. Sounds like the fuel ran out for sure.
     
    #6 The Professor, Oct 16, 2018
    Last edited: Oct 16, 2018
  7. bisco

    bisco cookie crumbler

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    might be wise to fill up sooner.

    i wonder why an empty gas tank can't produce an 'out go fuel message or something more comprehensible than steering power low.
     
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  8. fuzzy1

    fuzzy1 Senior Member

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    That was one of Bob's issues driving that thread. His older Prius, a Gen1, had such a warning. But Gen3 lacked it, and he was raising this issue as a safety hazard.

    How much fuel did you put in to refill after the previous episodes? Was it over 11 gallons?

    Also, was the last 75 miles this time a single or very few long run(s), or numerous short runs with numerous engine warmups?

    Those previous times were likely on or close to the hairy edge of empty. Then it doesn't take much extra in non-ideal conditions, or variations from prior conditions, to push you over the edge.
    Were the tires locked and sliding? Then the transmission's Park 'gear' was doing its job and is unlikely to be damaged. Slight flat-spotting on the tires ought to be the full extent of any 'damage'.
     
  9. William Redoubt

    William Redoubt Senior Member

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    My original 12 volt only lasted a year.
     
  10. The Professor

    The Professor Senior Member

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    ...and some will last 10.

    A lead acid battery in a car should last much longer than a year, unless something abnormal occurs, such as it not being kept charged properly, physical damage, exposure to temperature extremes, or it being defective.
     
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  11. Starship16

    Starship16 Senior Member

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    Why does someone, in a Prius or any car, drive it to the point of fuel exhaustion?! (Doing a one-time test is different.)

    Is it a matter of not having any gas money with you?
    Is it laziness?
    Just being foolish?
    Total inattention?
    Downright irresponsible?!

    Makes no sense to me.

    My wife would have kicked my A** and thrown me out of the car if I let the tank get that low! Especially with our baby on board!

    Stupid people like that need to get off the road.
     
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  12. Usle

    Usle Member

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    @The Professor, the car was a 12, so the 12v is 6 or 7 years old, and that's when the 12v needs replacement, allinall, the problem is fixed, moral being, check your 5 year old battery and trickle charge it periodically to keep it strong, then replace it at 6 years old.

    Ahh, as has been pointed out, a 16', back to the drawing board.
     
    #12 Usle, Oct 17, 2018
    Last edited: Oct 17, 2018
  13. Usle

    Usle Member

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    Any sign of rodents inside the car?
    Was the 12v drained over and over by leaving something on?
    Do you have a third party alarm?
     
  14. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    With stock size tires you won't have a problem. Oversize tires could create a problem.

    Old-timer recovery drivers usually have a bottle of dishwashing detergent on the truck. It's the perfect lubricant for dragging wrecked/locked tires without requiring its own cleanup after.
     
  15. Usle

    Usle Member

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    Really, an oversized tire drags differently than a stock tire?
    Why?
    The transmission is locked, the rubber is being dragged, the width of the contact patch matters not.
     
  16. fuzzy1

    fuzzy1 Senior Member

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    The OP lists it as a 2016, so it should be no-where near 6 years old.
     
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  17. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    If the tire diameter increases, you have a longer lever applying force against the parking pawl in the transmission. Eventually you'll break that lock. I'll grant you that this is very unlikely in a Prius as most owners keep stock wheels.
     
  18. Usle

    Usle Member

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    Yikes, her right, my bad, hmm
     
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  19. Mendel Leisk

    Mendel Leisk Senior Member

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    Running out of gas, in this age of credit cards, there's no rational reason to run the tank risky low.

    Regarding the 12 volt battery condition, forgedabout debate: just test it. Even a relatively new battery may be near-dead, due to lack of use, lights-left-on mishaps, whatever.

    A simple DIY test would be to check the voltage with a cheap digital multimeter, with the car off, first thing in the morning voltage. It should for sure be above 12.5, 12.6 is better, 12.7 and higher is in-the-pink.

    Better would be to do an electronic load-test. There's DIY testers for that, (Solar BA5) for example. Any battery retailer will probably do the same sort of electronic load-test for free, and dealerships will do it but likely incurring a diagnostics fee, say $50~100.

    And I'd second @bisco: it's ridiculous, that an out-of-gas car tells you there's low steering power.
     
  20. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Location: Ohio?
    Bay Area?

    You lost me a couple of turns back, but FWIW, I'll pile on.

    1.
    You ran out of gas.

    2.
    It wasn't a smart thing to do, especially considering your cargo, but I'll pull up short of calling you "stupid" myself because I'm sure that you will be reminded of this once or twice in the future.
    IF the "low fuel" light ever comes on again it will doubtless not be your only audio/visual warning if you have pax aboard.

    3.
    You didn't 'hurt' the car.
    The fuel pump is fine, you didn't hurt the transaxle, and other than domestic tranquility and some jibes from chuckle-heads on the internet, nothing really bad happened as a result of your misadventure except you're lighter in the wallet by $400.....which whether you're really in Ohio or you're in the "bay area" (Boston? Frisco? Hudson?) is cheap at the price.

    4.
    I run my car down to the point where the "low fuel" warning occurs, and then I run an additional 20 miles until DTE=0.
    Then?
    I start looking for a place to load fuel, KNOWING that I have at least a gallon and a half of fuel remaining, which even in a marginally maintained fleet Prius should be about 60-ish miles.
    If you sucked a tank dry before you thought you should YOU MAY HAVE OTHER PROBLEMS besides a tow bill, angry spouse, and some folks on the internet throwing shade on your fuel management practices!!!

    This bears immediate investigation.
    As a penance for your sins you should read a dozen or two "low oil" or "excessive oil use" threads.


    Good Luck!
     
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