Code reader can cause U0293 and other communication issues.

Discussion in 'Gen 2 Prius Main Forum' started by Adam Hamlin, Nov 29, 2019.

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  1. Adam Hamlin

    Adam Hamlin New Member

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    So the check engine light went on on my 2007 Prius,and I bought a code reader to determine the problem. The inverter water pump had failed, so I bought one and installed it myself. However, all of a sudden there were new codes being thrown along with the red triangle. UO293, U0100 primarily. The car would die and and the gear box would flash.

    I spent nearly a week pouring over potential issues, checking fuses, wires, etc etc. I was about ready to give up, so I did a mental checklist of everything that I might have touched or messed with after the original inverter water pump code that was no longer there because I fixed it. The only new variable was the code reader itself. Because I knew it was an information issue, on a hunch, I cleared the codes and quickly pulled the reader out after the lights went back to normal. I restarted the car, and the problem is gone. The code reader was actually causing the codes.

    Anyway, I just signed up and figured I’d share this because this forum has been such a help to me. I’m in between jobs and my little Prius is keeping food on the table VIA Lyft and I couldn’t aford expensive repairs and I was loosing work.

    I’m very happy for the help, and I wanted to do my part if someone else finds themselves in this problem. Thanks
     

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  2. sam spade 2

    sam spade 2 Senior Member

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    But maybe not in the way that you think.
    The ODB port is powered ALL the time. Leaving a reader plugged in will run down your 12 V battery.
    A weak 12 V battery can cause all kinds of random codes.
    How old is your battery ? Might be time for a new one.
     
  3. Adam Hamlin

    Adam Hamlin New Member

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    Thanks, yeah I charged the battery and ran a volt meter across it. It did shows a 12.71 or so, and the the check engine light would be on, I’d clear the codes and the car would run for 10 minutes or so before stalling and throwing all the codes.

    After taking it out, (It’s blue tooth to an app reader) everything is fine now. I drove it all evening just to be sure. I do hear you, and I’m going to replace the battery anyway, just Incase. Thanks for your input.
     
  4. davecook89t

    davecook89t Senior Member

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    When I first got my code reader, I thought I would just leave it plugged into the port all the time. After parking the car for about an hour, the ABS and Traction Control lights stayed on when I started it up again. Even when I unplugged the reader, they stayed on. Fortunately, they were gone when I shut the car down and turned it on again. Since then I have never left the reader in the port after the car has been turned off. Except for this one issue, the code reader (BASF) seems to work fine.
     
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  5. Adam Hamlin

    Adam Hamlin New Member

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    Yeah looking back the other codes literally started right when I was trying to figure out the other issue was (inverter pump), it’s what lead me discover the actual problem. I did not have an intention of leaving it in, but I was just trying different things, and clearing the codes to see if it were the problem, so the reader was in a lot. I had no idea that it could be the problem itself.
     
  6. PriusCamper

    PriusCamper Senior Member

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    I remember the first time I realized the OBD2 is always on... My carport is only five feet from my bed and I woke up one morning and picked up my phone and it was still on Hybrid Assistant app from previous night's work and to my surprise it was still connected and displaying battery voltage data. At least I made sure to turn the car off before I went to bed. Lol...

    Anyways, if you want to avoid the hassle of ever having to plug in or unplug your OBD2 reader you can buy an extension cord with a built in switch for less than $5 on ebay. I've never been able to find them domestically, but sometimes ordering from Asian markets only takes 10 days to arrive.

    Eventually I want to get one of these so I can stash everything behind the dashboard, mount the switch and forget about it: 16 Pin M to F With Switch OBD2 Cord Extension Cable Adapter Connector | eBay
     
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