Prius Gen 2 – P2103 after washing, engine won’t start, hybrid battery drains fast

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by BogdanB, Apr 22, 2026 at 8:12 AM.

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  1. BogdanB

    BogdanB New Member

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    Hi everyone,

    I’m having a recurring issue with my 2006 Toyota Prius Gen 2 and I’m hoping someone here has seen this before.

    Problem:
    After washing the car with a pressure washer, I get a Check Engine light and code P2103 (Throttle Actuator Control Motor Circuit High).

    At the same time:
    • The engine will not start
    • The hybrid battery drains very quickly (within seconds)
    • Multiple warning lights appear
    • Eventually the car won’t start at all
    It seems like the hybrid system is trying to run, but the engine never kicks in.

    History:
    This has happened 3 times so far:
    • The first two times, I left the car parked for 3–4 days
    • After that, it started normally again
    • Check Engine light stayed on briefly, then disappeared
    • Car ran perfectly afterward
    Current situation:
    This time, the engine no longer starts even after waiting.

    What I’ve tried:
    • Replaced the throttle body twice (no change)
    • Same P2103 code returns
    Observations:

    • Issue only appears after pressure washing
    • Seems strongly related to moisture
    • Temporary recovery in the past suggests something dries out and starts working again
    Questions:
    • Could this be a wiring harness issue?
    • Are there known weak points for water intrusion on Gen 2 Prius?
    • Could it be a bad ground or ECU connector?
    • Where should I focus diagnostics next?
    Any advice or similar experiences would be greatly appreciated.

    Thanks!
     

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    #1 BogdanB, Apr 22, 2026 at 8:12 AM
  2. bisco

    bisco cookie crumbler

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    welcome!
    are you pressure washing the engine bay? if so, I'd definitely say moisture, and it could be anywhere/everywhere.
    what are you reading the codes with?
    do you get the ready light when you power on? if not, it might be the 12 volt.
    you may have run the hybrid battery down trying to start it. sometimes, we think it started, but it's just spinning the engine.
    trouble shooting would be in the repair manual, but you need all the codes first.
    all the best!
     
    #2 bisco, Apr 22, 2026 at 2:14 PM
  3. ChapmanF

    ChapmanF Senior Member

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    Of course.

    As far as interpreting trouble codes, while I usually recommend not drawing conclusions from the one-liner fortune cookie at all, and just looking the code up in the repair manual to see what it actually tells you, sometimes it is helpful just to look closely at the fortune cookie.

    Notice this fortune cookie doesn't say the code is about the Throttle Actuator. Doesn't even say the code's about the Throttle Actuator Control Motor. It says the code is about the Throttle Actuator Control Motor Circuit. That includes all the wiring and connectors in that circuit, including the ones you are probably getting wet with your pressure washing.

    A trouble code about a throttle body control circuit is very likely about the wiring or connectors, not the throttle body itself ... especially if there's just been water shot in there ... and for sure, pretty much, if replacing the throttle body twice doesn't fix it.
     
    #3 ChapmanF, Apr 22, 2026 at 2:42 PM
  4. PriusCamper

    PriusCamper Senior Member

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    Can you please clarify what specifically you were pressure washing? As in, this is the internet and people are crazy and we even had a guy on here once who had pressure washed the inside of his car and didn't understand why he had error codes. Please be as specific as possible about what and how you pressure washed as well as what you did to protect electronic components from getting wet?
     
    #4 PriusCamper, Apr 22, 2026 at 4:03 PM
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