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

07 Prius Dead - Any Guesses?

Discussion in 'Gen 2 Prius Main Forum' started by jyl, Feb 1, 2010.

  1. jyl

    jyl New Member

    Joined:
    Nov 17, 2006
    84
    7
    0
    Location:
    Portland
    Vehicle:
    2007 Prius
    Well, our 07 Prius had its first problem after 45K troublefree miles.

    Wouldn't start. Engine Check light on. Then dash went completely blank. AAA came, put a portable jumper on the jumping point in the engine compartment, no change. We manually unlatched the hatch, AAA put the cables on the 12v battery, then the car started and would move under power, but the Engine Check light was still on. And, oddly, the gas gauge showed 1 flashing pip even though we'd filled the tank last night. My wife said enough is enough and had the car flatbedded to the dealer, and I took the kids home in my car.

    Any guesses? I initially thought a dead 12v battery, but wonder if it is something more than that. Hopefully it is something covered by the extended warranty . . .
     
  2. skruse

    skruse Senior Member

    Joined:
    Apr 6, 2004
    1,454
    97
    0
    Location:
    Coloma CA - Sierra Nevada
    Vehicle:
    2007 Prius
    Model:
    II
    The red triangle of death (engine warning light) showed up. I drove directly to the dealer. The dealer fiddled around for a week. I received telephone calls about what kind of gasoline, etc (clearly the dealer did not have a clue). Toyota engineers were finally called in. Problem solved: a single loose connection on the engine.
     
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    18,198
    6,461
    0
    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    It is highly likely that you need a new 12V auxiliary battery. The reason that the gas gauge is blinking one bar is because when 12V power is lost, the gas gauge loses its fuel level memory. It will take a few minutes to restore the correct reading.

    For future reference: when the car became READY after the jumpstart, you could have driven it, if the amber check engine light was the only warning light lit. Further, if the 12V battery is in good condition but just had a low charge, you could recharge it by leaving the car READY for several hours.
     
  4. jyl

    jyl New Member

    Joined:
    Nov 17, 2006
    84
    7
    0
    Location:
    Portland
    Vehicle:
    2007 Prius
    Thank you, Patrick.

    If that is it (not that I'm doubting), then I feel pretty silly. About a week ago I read here that a weak 12v battery could cause low gas mileage. Ours has been rather low, and I made a note to check the voltage on ours. What with one thing and the other, I hadn't gotten around to it . . .

    It is the original 12v battery, nearly 4 years old, and I've had to recharge it once before when the kids left the interior light on overnight. So, perhaps it was time.

    So, can you help me understand the meaning of the Engine Check light? Is the Prius smart enough that it will not permit itself to be driven if it has a fault serious enough to be unsafe to driver or car?

    Another question. I'm doubtful about my dealer's service charges - last month they wanted $400 to replace a broken rear light cluster, I told them no, bought a replacement off eBay for $105, and installed it myself in 15 minutes. $250+ rather steep for 10 minutes of mechanic time. So, I wouldn't be surprised if they wanted $400 just to replace the 12v battery. And, if I have the chance, I'd rather buy the battery - even from the dealer, it is only $130 - and install it myself. The question is, is it as simple as unbolting the terminals and bracket, replacing the battery, and bolting the connections back up? Or is there some complicated resetting procedure that would make it worth paying for them to do it?
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    18,198
    6,461
    0
    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    The check engine light comes on when the engine ECU logs a DTC. I normally would not expect that light to appear due to a weak 12V battery. However, it's possible that given the low voltage on the 12V bus, that a spurious error was logged that will go away after you disconnect the old battery (thus cutting power to the ECUs) and install the new one. Once you install the new battery, then you can see whether the check engine light persists, in which case you will have a second problem to solve.

    I'd encourage you to DIY install the new battery. It's not quite as simple as you suggest in your msg above, however.

    You'll have to remove the traction battery vent that runs over the 12V battery, and also move the brake power supply located next to the 12V battery. You can remove the hardware that secures the brake power supply, without removing the wiring harness connector. There's enough cable slack so that you can move the power supply an inch or so away from the battery.

    Pay attention to the various nuts and bolts as you remove them, so that you can put the correct hardware back in the correct locations.

    Then you'll have enough clearance to remove the terminal connections, battery bracket, and vent hose (suggest you remove the negative cable where it attaches to the body, rather than where it attaches to the battery) so that you can lift the battery out of the hatch area.

    Some owners get stumped by the red plastic terminal cover, trying to remove it from the fuse block. Just bend the cover up sufficiently so that you can access the nut securing the positive terminal.

    The fuse block will be attached to the battery bracket with a plastic clip. Rather than try to remove the fuse block from the battery bracket, just remove the whole assembly as one part.

    The battery vent runs into a rubber grommet located on the body, to vent hydrogen gas to the exterior. You can feel around with your left hand to locate that grommet in the body, if the vent hose pops free before you have a chance to see where the hose leads.

    Once the old battery is out, transfer the vent hose and the negative cable to the new battery, then reinstall. Make sure all electrical connections are tight, and that the bracket is snug (but not so tight that you risk cracking the battery case.)

    You'll need to reset the driver's window auto up/down function once power is restored. Make the window halfway open. Then close the window, and continue to hold the window button in the upwards position for a couple of seconds after the window is closed. Then the auto function should work. You'll probably have to reset your radio presets and you will lose trip odometer and possibly MFD mpg readings. You will also note your fuel gauge blinking one bar for a while, until that system figures out how much fuel is in the tank.

    Hopefully this provides enough guidance for you to be successful without spending lots of time on this project. Good luck.
     
  6. don_chuwish

    don_chuwish Well Seasoned Member

    Joined:
    May 1, 2009
    814
    180
    0
    Location:
    Southern Oregon
    Vehicle:
    2007 Prius
    Model:
    II
    +1 on the DIY. Once you get the floor out of the way and look at it for a few minutes you'll see how easy it really is.

    - D
     
  7. jyl

    jyl New Member

    Joined:
    Nov 17, 2006
    84
    7
    0
    Location:
    Portland
    Vehicle:
    2007 Prius
    Thank you, one and all. If the dealer gets all gouge-y, I am prepared!
     
  8. jyl

    jyl New Member

    Joined:
    Nov 17, 2006
    84
    7
    0
    Location:
    Portland
    Vehicle:
    2007 Prius
    Well, that was irritating.

    The car was flat-bedded to the dealer, who said the battery was low, but they recharged it, and say it took and held a charge. They supposedly "ran the diagnostics" and everything was fine. This cost $95. But they did send a car to pick my wife up at home, which was nice.

    Today (3 days later), the car was dead in our driveway. I left work, went by the dealer, bought a replacement battery ($138). Checked the original battery, it reads 5.6v, so dead as a doornail. I installed the new battery, took about 15 minutes, it arrived with 12.9v charge, the car starts up as normal.

    So now I am thinking, does it make sense that the original battery would go from re-charged to < 6v in 3 days? Does this suggest there is something wrong with the charging system?

    I think I'm going to buy a Scangauge.
     
  9. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    9,083
    5,795
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    I don't know whats wrong with your Prius, but Jim Lentz just came on Television and he say's he's sorry and suggests you call the 1-800 number...
     
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    18,198
    6,461
    0
    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    Thanks for the update; is your check engine light gone now?

    Your story illustrates why I believe it is a waste of time & money to pay for a dealer (or anyone else) to do a load test on the 12V battery. Too often you'll get a good health report, only to find that you have to replace the battery anyway. It makes much more sense to spend the $95 on partially funding the purchase of a new battery.

    I doubt that there's anything wrong with the Prius charging system. To verify this, all you have to do is to hook your digital multimeter (which I assume you own since you mentioned the voltage of your new battery and failed battery) across the battery terminals when the Prius is READY. If you measure ~13.8VDC then all is well.
     
  11. jyl

    jyl New Member

    Joined:
    Nov 17, 2006
    84
    7
    0
    Location:
    Portland
    Vehicle:
    2007 Prius
    Thanks, Patrick. The check engine light is off. I will check the charging voltage. Yes, I wish I hadn't spent the $95, but what the heck - this is the most trouble-free and cheapest-to-maintain car I've ever had.