Coolant Flow Valve and Battery Relationship?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Alex Priusfixer, Feb 19, 2023.

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  1. Alex Priusfixer

    Alex Priusfixer New Member

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    Hi y'all,

    I have been driving my 2005 Prius around with the check engine light and error code P1121 for about three years, no problem. The current battery is refurbished, 2 years old. Today all at once I got the master warning light and (!) brake error light (check engine light was already on). Ran the code scanner and got P0a80, P1121, P1123, and P0a80 Pd (pending). The p0a80 errors directed me to use the turn-headlights-three-times diagnostic menu to check my battery voltage, which showed:

    Acc mode: 11.9v
    Ig-on mode: ~11.7v
    Engine on: 14.4v
    The SOC visual shows battery charged halfway- I can't see how it behaves while I'm driving because the screen is mostly broken.

    Doing my research, I'm seeing a correlation between the Coolant Control Valve issues (P1121, P1123) and other users getting the same warning lights indicating battery issues. What is the relationship between these two problems?

    My second question of course is: what do we think is wrong with my car? The heat still blows fine. The acceleration feels off as described with dying battery issues, but this battery is young. Why is the resting voltage less than 12.0v after just 2 years, and based on the voltages I'm seeing- is the battery causing the master warning light? I'm willing to replace the coolant flow valve and see what happens, but want to cover my bases first and make sure I'm not missing anything. Any insight here is appreciated.
    Thanks,
    Alex
     
    #1 Alex Priusfixer, Feb 19, 2023
  2. dolj

    dolj Senior Member

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    None. If you fixed the P1121 when it came up, it would not be present now to cloud your thinking. There is no useful diagnostic information given by the warning lights other than to go look at what code that (or those) system (indicated by the light or lights) has set.
    More than likely your battery is failing and you will need to call on your battery supplier for a warranty replacement.
     
    #2 dolj, Feb 19, 2023
  3. Tombukt2

    Tombukt2 Senior Member

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    You're talking the 12 volt I'm assuming with the ignition on you're at 11.7 which is not 12 volts with the car running you're at 11.9 I think I saw I guess that's engine running car on and then something else at 14.4 or that's what the car is charging the 12 volt at which is about right so I would think running and on you would see the same 14.4 volts? Which is what you stated after I relook so with the ignition on and ignition off just at rest you're under 12 volts don't know how long it's been sitting like that but probably not that long and you're already under 12 volts My battery does similar 11 7 and 11 9... And I have no problems in the batteries about the same age right it two years so I would say you're 12 volt is probably reasonably okay unless it fails a load test 11.7 and 11.9 don't make me nervous given the two conditions and you have a full charge going on when the car is running and driving and it looks like it's able to hold it reasonably well what is your 12 volt voltage before first startup in the morning or whenever that is?
     
    #3 Tombukt2, Feb 20, 2023
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    Ignore the coolant valve codes, those are unrelated to the P0A80.

    That code plus weak acceleration point to a likely failing HV battery- which is not unexpected for a 2 year old refurb. Whatever was done to "refurbish" the pack, those modules are still used (who knows how many years old) parts.

    Use the search function, there are MANY posts for this concern. The most reliable option is to get a new OE battery.

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Feb 20, 2023
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