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Advice on Possible Hybrid Battery Failure

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Brooke D, May 6, 2015.

  1. Brooke D

    Brooke D New Member

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    2004 Prius
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    N/A
    Hi folks,

    Sorry for this long post. But I would appreciate your thoughts and advice on a possible hybrid battery failure in my 2004 Prius (96K miles).

    Sunday before last, the check engine light, warning triangle, and hybrid warning light came on when I started my car at the grocery store.

    Because I was close to home, I drove home and the car functioned completely normally. The next morning, when I started the car, the same warning lights appeared. However, when I tried starting my car with the headlights off (I always leave them on), no warning lights appeared.

    I took my car to an independent mechanic. This is their written report:

    "Found multiple check engine codes, P3000, sub code 123, V0100 sub code 211/330. These codes are set when high voltage control detects a malfunction in battery pack/ECU assembly. To check battery pack we took vehicle out on a test drive while monitoring the cells in the battery pack. Found that they are all weak and drop fast when battery is put under a load. Code C2318 is a low voltage error/power supply malfunction code with the auxiliary battery. The voltage spec for setting the code is 9.3 volts, this battery is less than 9.2 volts."

    In conversation, the mechanic also told me there was significant voltage variation across the cells in the hybrid battery.

    I then took my car to the dealer to try to confirm this analysis. They were unable to read any codes because the independent shop apparently cleared them. The dealer was unable/unwilling to do more than read the codes to diagnose the problem. (Indeed, they seemed surprised that the independent mechanic could monitor the cells in the pack.) All they did was to drive the car around some more to see if the check engine light would come on. It did not.

    The car has been driven 80 miles since the warning lights last appeared and appears to be behaving normally.

    From your perspective, does the report from the independent mechanic make sense and is it believable? And is their test under load definitive of a hybrid battery problem? Could the results be affected by the low auxiliary battery?

    Also, if I do have a hybrid battery problem, what are the chances of being suddenly thrown into limp mode while driving it? This is what worries me the most: if I decide not to fix the car and to buy a new/used car, I'll need to be driving around to dealerships or individual sellers. Some of these sellers might be "over the hill" from here--which means driving from Santa Cruz to Silicon Valley over Highway 17. Those of you who are familiar with the area undoubtedly understand why the thought of going into limp mode on that road scares the heck out of me. Basically, I need to decide whether or not to rent a car if I have to drive over the hill.

    Any advice/opinions would be appreciated. If anyone in the area knows of other options for replacing the hybrid battery other than shelling out the $3500 the independent mechanic and the dealer want, I'd also be interested in hearing about that.
     
    #1 Brooke D, May 6, 2015
    Last edited: May 6, 2015
  2. koolingit

    koolingit Member

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    Replace the 12 volt battery and all will be well. Make sure the new battery is fully charged before installing.
     
  3. exstudent

    exstudent Senior Member

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    P0A80 is the typical DTC logged for a bad HV Battery. Bad meaning a module or two, are out of specs, triggering the DTC. The other modules that are fine for now, may not be far behind either. Thus the problem of swapping out bad modules. Its a temporary, unreliable, but cheap fix; would hate to be stranded due to the other modules going bad.

    A NEW HV Battery pack from a Toyota dealer who sells on-line, is $2000-$2400. You have to shop around and make sure they will sell to you, as there have been reports of these same online Toyota dealers won't sell to a lay person, who isn't a mechanic or a auto parts store employee. You will also have to pick-up the HV Battery as most dealers won't ship this item; best to bring your core at the time of pick-up too, to save a return trip.

    There are 20% off retail parts coupons from Toyota dealers, so search around dealer websites; dealers usually match other dealers parts/service coupons.

    Call Luscious (San Francisco) and Art's Automotive (Berkely), for pricing of a NEW HV Battery.
     
  4. Eclipse1701d

    Eclipse1701d Prius Enthusiast

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    Three Touring
    At 11 years old, it is very possible that your HV pack has some anomalies. However, you could be lucky and have a low 12Volt battery, or a failing inverter pump. With the car in ready (on) and in Park. Open the hood and check the inverter fluid reservoir for turbulence. No turbulence represents a failed pump. This is a long shot, but I would at least check it out. A 12Volt and a pump is a lot less expensive than an HV pack...

    On a side note, I cannot stress enough how important it is to check one's HV Battery Fan for debris. I think this is often overlooked and a failing or clogged fan can definitely stress out the HV Battery if it cannot cool the pack when needed. Please people, take an hour to remove the rear passenger side molding on your Gen II's and clean you HV fan every few years... Especially if you have pets in the vehicle!
     
  5. Brooke D

    Brooke D New Member

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    Vehicle:
    2004 Prius
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    N/A
    Hi folks,

    Thanks for your replies so far.

    So it is possible that the 12V battery is the culprit? Could it cause the mechanics to get misleadingly low readings or inconsistent voltage readings on the hybrid battery?

    Brooke
     
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Two
    Your 12V battery definitely needs to be replaced. It is possible that the low voltage may have caused a temporary fault in the traction battery ECU which is responsible for tracking module pair voltages in the traction battery.

    So, start with replacing the 12V battery, then see what other issues still exist.

    You say that you have driven 80 miles since the warning lights last appeared - are the warning lights still on now? You also say the car is behaving normally, so I take that to mean you are not aware of any driveability symptoms such as lack of power or abnormal noises.

    Regarding limp mode, if the traction battery has a bad module, then it will deteriorate to the point where the car will enter a limp-home mode. However at this point if you don't notice any driveability issues then it is premature to say anything is wrong with the traction battery.

    If you get Mini VCI, you can be self-sufficient with regards to retrieving DTC logged by the car and will not have to rely on a dealer to pull those codes for you.
     
    koolingit likes this.