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"Check Engine light" correlate w/ low gas?

Discussion in 'Generation 1 Prius Discussion' started by ElizaDay, Jun 12, 2010.

  1. ElizaDay

    ElizaDay New Member

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    I have had two CEL issues, both involving my gas cap. First time, silly me didn't have the cap on tight enough. Second time, the cap was bad and needed to be replaced. Today, I ended up getting lost in the country, couldn't find a gas station and was dangerously low on gas. I was on the low bar for about ten minutes and then the check engine light went on.

    Given my history with the CEL light and gas, I'm wondering if this could be related? I filled up the tank and the Check Engine Light is still on.

    I have a 2001 Prius (1st gen).

    Thanks,
     
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Turn your car off-and-on three times. This should clear the "Check Engine Light" while leaving the code(s) that triggered it. But this leaves open, what are the code(s)?

    Now there are several approaches:

    • ~$100 - visit a Toyota service center and have them read out the code(s). Might as well ask for the traction battery voltages at the same time. They will tell you what the codes mean but bring them here and we'll double check against past practices.
    • ~$50-$250 - buy an ISO 9141 compatible, over the counter, scanner and read out the codes directly. But I've found the available, low priced units to be not so good.
    • $300 plus laptop - Auto Enginuity can be used to read codes IF you pre-configure the interface for ISO 9141. However, if operated per current instructions, it will spike the controllers and lead to false codes. (NOTE: there is an adapter that prevents Auto Enginuity errors.)
    • Tc/Ts code flash - there is one pin, Tc, tied to chassis ground will cause the ECUs to flash two-digit versions of the codes. Although built-in to the Prius, it is not easy to access the connector.
    Try the three-start first to see if the check engine light goes out. Since you live in Florida, between now and when you need to get your vehicle inspection, choose one of the above options.

    GOOD LUCK!
    Bob Wilson
     
  3. TexomaEV

    TexomaEV Member

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    Autozone & or O'Reilly's Autoparts have scanners they will let you use, or help you read what the codes are from your vehicle's ODBII diagnostic port. Just make sure and ask if the code reader is the compliance certification, Mr. Wilson mentioned in his response. The unit O'Reilly's had in my area had several ODBII adapter cables, one for just about every make/model vehicle out there.
     
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  4. ElizaDay

    ElizaDay New Member

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    I'm actually not in Florida anymore. I'm in Northern California. I actually have a mechanic here but he is closed until Monday. I was just wondering if there could be any relation between the low gas and the check engine light.

    I also have restarted my car more than three times and the CEL is still there. Does this mean that it's not related to the low gas?

    Thanks,


     
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    It suggests either the problem continues and/or a code sufficiently severe that the normal three-times restart isn't clearing the check engine light. TexomaEV has a reasonable suggestion and a quick visit to an autoparts store would be easy enough . . . piece of mind until you can visit your mechanic.

    I didn't mention renting a Graham miniscanner but I don't think it makes sense in your case since I can't get it out there before you'd be able to visit your mechanic. It really works best for those who are working on a rebuild and aren't ready to go with an Auto Enginuity.

    Now if you feel adventerous, you could try Tc and tie it to ground:
    [​IMG]
    You would need to push one wire into the diagnostic port, pin 13, the right-side connector, found under the dash just to the left of the steering column. The other end goes into chassis ground, pin 4. Turn on the car and start reading the blinking light codes from the dash lights. But it is hard to see the connector and hit the right pins:
    [​IMG]
    Still, the price is right. <grins>

    Bob Wilson
     
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  6. jk450

    jk450 New Member

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    Probably not. However, it is difficult to know for sure without looking at the code and the associated data.

    It means nothing. In the case of your car, restarting it any number of times will have zero effect on the warning light. I have no idea why you are being told otherwise.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If the problem that caused the CEL to turn on is still present, then the CEL will remain lit regardless of the number of times the car is restarted. If the problem no longer is present, then the CEL will eventually turn off.

    It does sound like the OP's vehicle has a problem that is more serious than a loose fuel cap or low fuel, so I encourage the OP to obtain the DTC soon.
     
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  8. jk450

    jk450 New Member

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    It depends on the situation. There are many different factors that can affect that. However, for the sake of brevity, I'm addressing the OP's situation, rather than general operation strategies.
     
  9. statultra

    statultra uber-Senior Member

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    To make it real simple, i know Autozone does free diagnostic checks, if theres one by you go there and ask them to check the codes. Usually check engine lights on the Prius are DTCs set in the ECM


    I had a check engine light because my mass airflow sensor was dirty, just a quick cleaning and the engine light never came back. The code was something like lean condition.
     
  10. ElizaDay

    ElizaDay New Member

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    Thanks everyone for your feedback. FYI, the mechanic ran the diagnostics and determined that the CEL was on as a result of the low gas.