2005 - No error codes but won't go ready - traction battery is low

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by NoTrueScotsman, Dec 15, 2021.

  1. NoTrueScotsman

    NoTrueScotsman New Member

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    thanks to everyone who helped me on my previous thread regarding my 2005 Prius:

    (2005) random negative voltages on hybrid battery modules from OBD + P3030 | PriusChat

    The battery wiring harness and ECU were indeed fried and I've replaced both of those.

    After doing so I cleared error codes, disconnected and reconnected the 12v battery. No error codes present via OBD now (and no warning triangle or "error" on touchcreen). Electrical system comes on just fine, but the car will not go into 'ready' or start the petrol engine -- even if I turn on the heater, which normally forces it on. The traction battery charge level is showing the lowest state (1 bar). This would make sense as I was unable to start the car for some time.

    Also my OBD reader shows 13 - 14V for all battery modules, except number 1 and 2, which are showing 9V and 11V.

    Does anyone know if I will definitely have to tear down the battery and replace modules 1 and 2? (I've done it before, and it's not out of the question, but it's a massive pain). If so, why aren't I getting the orange triangle of death and error codes?

    Or is there a chance that the traction battery is simply too flat to start the engine and needs to be manually charged with some sort of special charger? Can Toyota do it? Or both problems at once?

    I would take it into Toyota but I'll have to pay a fortune to get it towed there so I'd like to not waste a trip if possible.

    Thanks for reading.
     
  2. bisco

    bisco cookie crumbler

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    perhaps you cleared the codes too soon, what are you reading them with?

    yes, toyota does have a special charger, or you can buy a grid charger. you can flatten the battery if you try to start the engine for too long.
    but if the engine wouldn't start, perhaps it is a different issue
     
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    Also my OBD reader shows 13 - 14V for all battery modules, except number 1 and 2, which are showing 9V and 11V.

    If this is true then your HV battery is pretty much completely depleted. Remember, one block is actually 2 modules. These individual NiMH modules have a voltage plateau at 7.2v. This is why 7.2 is considered 'nominal' voltage. That's 14.4v per block. and about 202 volts for the entire pack. Most packs spend their entire life in the 210-220 volt range during normal operation. If you're at 14v or less per block, well, it's at an extremely low state of charge and that's very likely why the car will not go to ready condition.
     
    m.wynn likes this.
  4. 2010moneypit?

    2010moneypit? Member

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    Sounds like you need to get a grid charger if it all possible. If you take it to Toyota they will probably tell you you need a traction battery. Although you may need one you will not know until you properly balance the traction battery that you currently have.
     
  5. Fred_H

    Fred_H Misoversimplifier

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    Oops. Sorry, I wrote something here by mistake.
     
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