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Prius quite running and won't start with codes U0073, U0123, U0124, U0126, U0293, POA72

Discussion in 'Gen 2 Prius Main Forum' started by Enoch Mease, Jul 22, 2022.

  1. Enoch Mease

    Enoch Mease New Member

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    Hello, I was driving today in my 2005 Prius with about 280k miles and the red triangle appeared, then the car died and won't start. The codes U0073, U0123, U0124, U0126, U0293, POA72 came up on the health check with Techstream. It has a strong 12v and HV battery. Would anyone know what could be wrong and how I could troubleshoot? Thanks
     
  2. PriusCamper

    PriusCamper Senior Member

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    I always say a lot of codes all at once for the first time is usually something that's gone unplugged, or a fuse that needs to be replaced or bad 12v or its connections... How many miles? Any recent maintenance or other symptoms?

    Once you check everything for the obvious clear the codes and let us know what comes back first and how quickly it happens.
     
  3. ChapmanF

    ChapmanF Senior Member

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    As you are using Techstream, you have an advantage here: the health check screen shows the codes grouped by which ECU reported them. You can help us out if you preserve that information for us when you post it. That is especially important for all U codes, because those are communication codes, and they mean that something in the car can't communicate with something else. The code itself tells you what the something else is, and the something is the ECU that reported the code.

    Also, it's handy to know that the second character of a code won't ever be the letter O because it can only be digit 0, 1, 2, or 3. So if you search a forum or the internet for P0A72, you are likely to get more search results and better ones than if you type it as POA72.
     
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  4. Enoch Mease

    Enoch Mease New Member

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    Thanks for your response. I bought it with a bad HV battery and don't know it's history. The check engine light was on but it drove fine for about 150 miles after replacing the HV battery. The fuses all look good. I'll take a look around again to see if I can see anything that might be unplugged.
     
  5. PriusCamper

    PriusCamper Senior Member

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    If you don't have a way to read & clear codes you can disconnect 12v battery for a few minutes to clear them. But getting a Mini-VCI plug for Toyota Techstream or an OBD2 plug for phone apps to read & clear codes should be a high priority. Let us know if you need help with that.
     
  6. Enoch Mease

    Enoch Mease New Member

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    That's really helpful ChampmanF, about the meanings of the code numbers and letters. Does this mean that a ECU may be the problem? Can I use Techstream to troubleshoot? How would you go about finding the problem? The fuses are good and the 12v batteries at 12.73v.
     
    #6 Enoch Mease, Jul 22, 2022
    Last edited: Jul 22, 2022
  7. Enoch Mease

    Enoch Mease New Member

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    It looks like the codes are coming from the ECU ABS/VSC/TRAC.
     
  8. Tombukt2

    Tombukt2 Senior Member

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    Yes it sounds like that maybe the case so you should have the red brake light the VSC and I don't think your car will have traction control but I'm not sure about that and they should never go out does your brake pedal feel like it's working properly I drove my car for almost 2 years with the ABS VSC which is vehicle skid control and the red brake light like the parking brakes on for that whole time and the brakes worked perfectly I had no ABS. But the brakes work just like a Corolla four-wheel brakes without ABS if I stepped on the pedal too hard I could smoke all four wheel wells looked really cool but that was about it. So you may well have a bad break will call it the actuator which is the part with the pump that makes all the noise it whines when the car starts is turned off two of mine have done this exact same thing I just fixed the '09 days ago successfully good luck
     
  9. Enoch Mease

    Enoch Mease New Member

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    What you described sounds like what is happening with my prius. The brake light, traction control, ABS and the red triangle comes on when I try to start it. Do you think the actuator needs replaced? I have another prius that I can take parts off of. I've heard that the lateral accelerometer and yaw rate module often go out and somebody told me that they may be the problem?
     
  10. Enoch Mease

    Enoch Mease New Member

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    Do you know how to narrow down which ESU is having communication issues or needs replaced? Can I use Techstream to find which ABS/VSC/TRAC ESU is causing the problem? Could it be the actuator? What would you do? Thank you guys for your time!
     
  11. ChapmanF

    ChapmanF Senior Member

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    Do you think you could find a moment to double check? Sometimes people post a screenshot of their health check screen so we can all have a look.

    I wouldn't always doubt what you said, but I didn't think P0A72 was an ABS/VSC/TRAC code, so something strikes me as fishy.

    The place you can find all the diagnostic info you're looking for, and what to do to understand the codes, is the repair manual, as described here:

    Toyota Service Information and Where To Find It | PriusChat

    When you post the codes and information here, we can often offer some pointers; it's fun to help out. But ultimately we're giving you the same information you can find in the repair manual, so if you ever get impatient waiting for us to reply, or you just want to get a more first-hand grasp of the info, it's never a bad idea to look there.

    For U codes, especially, the troubleshooting can be kind of involved. There's a lengthy section in the repair manual about it, and you might find it easier to have that in front of you than to do a whole lot of back-and-forth on the forum.
     
  12. Enoch Mease

    Enoch Mease New Member

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    Thank you for pointing me to the repair manual. It helps lots although I probably don't understand most of it : ) It looks like all the U codes that I got communicate from the Skid Control ECU. I was thinking that may be the problem then I noticed that the connection for the fuses under the hood are corroded. Especially the HEV fuse. So I'm going to replace the black rectangle fuse connector box and see if that's it.
     
  13. Enoch Mease

    Enoch Mease New Member

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    I put in a new skid control ECU from another prius but the engine still won't turn on. Also, the red triangle stays on. However, it will drive down the road but sense the engine won't run I don't want to drain the HV battery. I'm able to get any part that I want from another Prius. If anybody has any suggestions let me know? Thanks
     
    #13 Enoch Mease, Jul 23, 2022
    Last edited: Jul 23, 2022
  14. ChapmanF

    ChapmanF Senior Member

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    The more we know about the codes you currently have, and which ECUs are reporting them, the more we can offer as you diagnose your situation.

    It's possible the codes now might not be the exact ones you had before the recent part replacement.
     
  15. Enoch Mease

    Enoch Mease New Member

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  16. Enoch Mease

    Enoch Mease New Member

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    Let me know if you need anymore information. I really appreciate the help.
     
  17. mr_guy_mann

    mr_guy_mann Senior Member

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    Ok. So if we look at the codes, AND we look at the ecu's that didn't report on the health check, it looks like something is wrong with the CAN communications network.

    Some ecu's only use CAN to talk with other ecu's (ie, function) and then use another network - SIL - to talk with a scantool (diagnostics) Others (ECM, Hybrid Control, and HV battery) use CAN for both function and diagnostics.

    The ABS ecu can't talk to most anything else (except a scantool on SIL). ECM, HC, and HVb can't talk to a scantool (on CAN). But at least HC and HVb can talk to the rest of the car (on CAN)- otherwise the hybrid system would be dead.

    Put it all together and I expect that there is a damaged CAN wire or poor connection somewhere. The codes might suggest that it could be "between" the DLC/OBD2 connector and the steering angle sensor. Possibly Junction Connector 1? You have to get wiring diagram and start checking.

    A preliminary test is to disconnect the 12V battery then use a multimeter to test the resistance across pins 6 &14 of the OBD2 connector. Do not jam the meter tips into the terminals- you can damage the the connector. Gently touch the tips to the metal terminals. Resistance should be around 60 ohms.

    Posted via the PriusChat mobile app.
     
  18. mr_guy_mann

    mr_guy_mann Senior Member

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  19. mr_guy_mann

    mr_guy_mann Senior Member

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    edit:

    couldn't quite see in the first picture - but the health report DOES show the HV battery ecu. Doesn't change my opinion that something's wrong with CAN. Might be a missing power or ground to the ECM.

    Posted via the PriusChat mobile app.
     
  20. BillMelder

    BillMelder Junior Member

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    Any updates on this? im having the same issue with codes popping up u0123, u0124, u0126.

    2009 Prius 157,000 miles