P0303 Code

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by veggiecar, Feb 16, 2026.

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  1. ASRDogman

    ASRDogman Senior Member

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    That's good. But you don't know what the issue was....
     
    #21 ASRDogman, Feb 19, 2026
  2. rjparker

    rjparker Tu Humilde Sirviente

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    It was the #3 coil
     
    #22 rjparker, Feb 19, 2026
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  3. veggiecar

    veggiecar Junior Member

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    Here we are about five and a half months later. My son started the car last night and I heard the motor shutter and shake for a moment and then ran smoothly. When he got home the check engine light was on. The code was p0300, p0302, p0303, p0304. I cleared the code and restarted the car and without any misfires the same codes reappeared. Five months ago I replaced the spark plugs and coils from amazon. Marsram Ignition Coil UF596 Spark Plug. Amazon said they would fit my 2012 Prius. Is it possible that these parts are substandard or is there another potential explanation. Thanks so much for the help…
     
    #23 veggiecar, Aug 3, 2026 at 7:21 PM
  4. ASRDogman

    ASRDogman Senior Member

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    It is VERY likely you got cheap chinese copies. Surprised they lasted that long.
    Do you still have the OEM coils? If so, put them back in.
    Go to autozone and get the Bosch Double Iridium spark plugs.

    NEVER buy electrical parts from ebay or amazon. 99% of them are cheap chinese copies.

    And you still don't know what the cause of the problem was/is.

     
    #24 ASRDogman, Aug 3, 2026 at 7:58 PM
  5. veggiecar

    veggiecar Junior Member

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    I could put the plugs back in but one of the coils is definitely bad. I will get a name brand product.
     
    #25 veggiecar, Aug 3, 2026 at 10:38 PM
  6. ASRDogman

    ASRDogman Senior Member

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    There is no sense in getting a cheap ones.
    Unless you like taking the wiper assembly apart....

    I know it cost more to get the parts from Toyota, but at least you know they are good parts.
    And you won't have to change them again for 100,000 miles. And maybe never for the coils.

     
    #26 ASRDogman, Aug 4, 2026 at 7:18 AM
    Last edited: Aug 4, 2026 at 12:11 PM
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  7. BiomedO1

    BiomedO1 Senior Member

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    The morning shutter and shaking doesn't bode well. Did you test for head gasket failure and did you keep the old parts? I'd stick with the OEM stuff - proven track record. I toss them when I know they are bad and use them for troubleshooting; when I suspect an issue. This is better than throwing Amazon or Ebay parts at a problem...... IMHO
     
    #27 BiomedO1, Aug 4, 2026 at 11:02 AM
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