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Master warning and malfunction lights

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Nelson12, Aug 2, 2021.

  1. Nelson12

    Nelson12 New Member

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    Hi everyone. I’m the owner of a 2nd gen Prius from 2007. I’ve had a problem for around 5 years that I’m hoping you can help me with. Once in awhile, probably 5-10 times a year and often close together, the Master warning and malfunction lights will come on. The sequence will be: while driving, the car will suddenly have a small hiccup (feels like there’s a problem with the cooperation between the gas and electric engines taking over from each other (sorry, I’m really bad at the tech of it)), the warning and malfunction signs will come on and the the car will switch to only electric driving, meaning that once the battery has been emptied the car will stop. The solution will be to pull over, turn the car off and the back on again, which will make the car run again with both fuel and electricity being used. The warning lights will still be on for one or two drives, then the master warning light will disappear and after a couple more drives the malfunction light will disappear as well. I did take the car to the dealer for them to fix it, and they told me they did some tests and a reset of the car, but that if that didn’t solve it they’d have to replace the battery. The reset didn’t fix it. The problem is that I don’t really think they know what the issue is, and that changing the battery won’t fix it. As far as I can tell the battery seems to have fine capacity. And I’ve read on forums about people who’ve had warning lights come on, then their expensive battery replaced, but not the problem fixed. The issue has happened 4 times within the last two month, which is more than usual, and I just had service performed 2 months ago. Also, not long ago they did the hybrid health check, which came out fine. I would so, so much appreciate any input, as I would hate for them to exchange the battery and pay a small fortune if that’s not the actual problem. Kind regards and thanks in advance.
     
  2. ChapmanF

    ChapmanF Senior Member

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    When those lights come on, the car stores diagnostic codes to report why.

    The most important thing you can do is have those diagnostic codes read while those lights are on.

    If it has been happening occasionally and it hasn't been convenient to have a dealer read the codes while the lights are on, you might simplify your life by equipping yourself to read the codes the next time it happens. Many on these forums will use a beater Windows laptop and Toyota's Techstream software, though that isn't the only option. If you go with some other option, though, you want to be sure that it can read diagnostics from all the ECUs present in a Prius, because not everything can. Having warning lights on and the code reader you're using telling you "no codes" is a situation you want to avoid.

    Yes, regrettably, that kind of outcome isn't uncommon when people guess at what their warning lights mean rather than getting the diagnostic codes.
     
  3. PriusCamper

    PriusCamper Senior Member

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  4. bisco

    bisco cookie crumbler

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    welcome!
    there is no reason a dealer in denmark cannot read the codes. if you paid them to diagnose, ask them what the codes were, and post them here.
     
  5. ChapmanF

    ChapmanF Senior Member

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    Something is rotten ....
     
  6. TMR-JWAP

    TMR-JWAP Senior Member

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    At the risk of stating the obvious, or essentially guessing, it sounds like an 'engine failed to start' situation. P0A0F.