Lack of check engine light

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Darcy851, Jun 14, 2026 at 2:32 AM.

  1. Darcy851

    Darcy851 Junior Member

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    I've always passed California smog with no issues, but this time failed because my check engine light doesn't illuminate in maintenance mode. Looking back, I can't remember whether I have ever seen my check engine light turn on. I bought my car from a questionable seller 5 years ago, and I wouldn't be surprised if they somehow tampered with the check engine light. Does anyone have suggestions about where I should check to see if they disconnected it? I know that in the Gen 3s the check engine light is an LED, so they couldn't have just unscrewed a bulb. Maybe they snipped a wire? Does the check engine light plug into the ECUs behind the glove box?
    Thank you for any advice.
     
    #1 Darcy851, Jun 14, 2026 at 2:32 AM
  2. Mendel Leisk

    Mendel Leisk MMX GEN III

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    I’ve had ours in maintenance mode a few times, can’t recall if it lit the check engine light. Was the inspection at your usual place, seems kind of sketchy.

    Google AI mentions specific lights that WILL come on, but not CEL:

    https://share.google/aimode/KiyBXplKm9O08RDlZ

    if I’m ambitious I might test it, but currently have some woodwork project headaches on the go. :)
     
    #2 Mendel Leisk, Jun 14, 2026 at 7:58 AM
    Darcy851 likes this.
  3. ChapmanF

    ChapmanF Senior Member

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    #3 ChapmanF, Jun 14, 2026 at 8:16 AM
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  4. rjparker

    rjparker Tu Humilde Sirviente

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    I doubt the emissions inspector put it in the Prius specific maintenance mode.

    Even if he did, the check engine light is off in that mode.

    Ignition On, two presses without the brake, illuminates the check engine light among others.
     
    #4 rjparker, Jun 14, 2026 at 1:37 PM
    Last edited: Jun 14, 2026 at 2:55 PM
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