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P3125 and no start, 2003 Prius

Discussion in 'Generation 1 Prius Discussion' started by skepticdoodle, Aug 12, 2024.

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  1. skepticdoodle

    skepticdoodle New Member

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    Vehicle:
    2003 Prius
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    N/A
    Long story short, I purchased a 2003 Prius for $500 on Wednesday (8/7/24) in a brick condition. The car had no power whatsoever, did not start or do anything. The previous owners claimed that the 12v died and they replaced it and now the car was a brick. It seems as though the hooked the battery up backwards or jumped it incorrectly or something, causing a number of issues. The only thing that worked was the map light. Made the very excellent decision to purchase the vehicle and towed it home.

    Started as anyone does with weird electrical issues, at the fusebox(es) and 12v battery. The 12v was dead and determined to have a dead cell after attempting to charge. There were 4 fuses blown, consisting of the main 100a fuse, the 30a RDI fuse, the 15a AM2 fuse, and the 15a THRO fuse.

    I replaced all of the blown fuses (the 100a one was so much fun), tossed in an ill-fitting placeholder battery from another vehicle and the car fired right up and seemed to run well. At this point I noticed that the MFD turns on but doesn't display anything relating to flow of electricity and is locked at 99.9 mpg. The outdoor temp section is also just blank. The radio does not function and neither does the clock or anything other than climate control in the center control area. Based on my research this seems like a bad gateway module, of which I have another to put in. This, however, is just the beginning. I was able to drive the car around my driveway with no issues.

    After the car warmed up, the red triangle and check engine lights came on. I used my cheapo auto parts store scanner to scan the computer and it did not show any codes. I attempted to restart the car to see if the issue persisted, which it did. I scanned the computer again which once again read nothing. After a quick google, it seemed as though this could be caused by low oil or coolant. The oil level was good, but the coolant was quite low so I assumed that was the issue. After topping the coolant off the next day I attempted to fire the vehicle up again, which it did.

    I did have the 12v disconnected overnight, which seemed to clear the codes and things were well for a bit until the check engine and red triangle lights came on again, only this time, the motor revved up and the car seemed quite unhappy in general. I scanned the computer before shutting it down, I scanned the computer again to which I saw P3125, inverter malfunction. This was the last time the car ran. I attempted to restart it to see if I could move it to a better place, but to no avail. The car makes a click or two and says "READY" for a moment before failing to start and giving the red triangle and check engine with P3125.

    So, I did quite a bit of research and planned on doing more proper diagnosis, until yesterday morning I was in a gambling mood and found another 2003 at my local pick and pull with only 85k (mine has 160k). I took it's inverter for $100 and installed it the same day to which I am greeted with identical symptoms (oh well, that was the gamble). So far, I have rechecked all fuses and tried a different 12v which got me nowhere.

    Today, I ordered a Veepeak OBDCheck BLE + scanner and purchased Torque Pro, downloaded Dr. Prius, and Hybrid Assistant. I could not figure out how to make Torque Pro read the sub codes on the first gen that I have so any help there would be great. Dr. Prius and Hybrid Assistant gave me errors trying to read the data coming from the car, and both gave me N/A values for all of the hybrid things. All other readings worked correctly. Not sure if this is user error or an issue with possibly the HV ECU?

    I was hoping to avoid Techstream since I was having issues getting my vm to work, though I can work that issue if necessary.

    Any assistance would be great. Really hoping this isn't one of the MG's. I'd like to diagnose properly before partaking in more gambling. I have yet to check the individual cells of the traction battery with my multimeter.
     
    #1 skepticdoodle, Aug 12, 2024
  2. skepticdoodle

    skepticdoodle New Member

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    Forgot to mention that I had driven the car less than half a mile total and had it running for less than 45 minutes total over the multiple times it ran.
     
    #2 skepticdoodle, Aug 12, 2024
  3. ChapmanF

    ChapmanF Senior Member

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    For any project Prius bought in brick condition, you're definitely going to want a scan tool (whether Techstream or some equally-functional alternative, if there is one) that can show you all of the codes and subcodes, freeze frames and live data lists.

    P3125, if I remember right, is a gen 1 code for anything involving the inverter/converter, and has something like a gazillion different subcodes distinguishing the actual problem. (By the time later generations came out, the SAE had created a whole bunch of different standard P0 codes for different inverter/converter issues, and Toyota retired the P3125 code and assigned all those different issues the gazillion different P0 codes that were newly standardized.)
     
    #3 ChapmanF, Aug 13, 2024
  4. skepticdoodle

    skepticdoodle New Member

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    Vehicle:
    2003 Prius
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    So I felt like doing a bit more gambling this morning, and acquired a new HV ECU, and now the Dr. Prius app will read the HV battery instantly. The car still doesn't crank or start. The red triangle is gone and there are no codes after a number of attempted starts. I have three traction battery cells that are WAY below the others.

    I assume a safe next step would be charging/replacing these low modules?

    I hear you on the Techstream front, but I've still been unable to get my XP vm to work with my laptop. I may need to find a cheap older laptop to get it to work correctly.
     

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    #4 skepticdoodle, Aug 13, 2024
  5. mroberds

    mroberds Member

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    The two Gen1 PID files for Torque Pro that are/were floating around had a couple of typos, at least back in 2018.

    This post has links to the two PID files: Torque PIDs for Gen1 Prius | PriusChat

    This post explains the typos I fixed: Scangauge or Torque App? | Page 7 | PriusChat

    Once I fixed those, the then-current Torque Pro could talk to my 2001, through one of those generic Bluetooth OBD-II scanners.

    I once thought as you do. Get Techstream. :D

    A safe next step would be getting Techstream. :D

    If you want to try charging the modules in situ, I would disconnect the 12 volt battery, remove the service plug from the HV battery, unplug that orange connector from the battery ECU, and disconnect the two main cables from the HV battery. This makes it so the module stack is definitely disconnected from anything else, so your charger won't send voltage into any strange places. Make sure you trust the limits/shutoffs in your charger, and check on it often.

    It doesn't take a lot. When I first got Techstream in 2018, I ran it on a desktop PC that was the Wal-Mart Black Friday special in 2004. :) It had XP patched up through the end of support, Athlon XP 2.0 GHz, and 0.5 GB of memory.

    It was a pain in the butt to haul the PC and monitor out to the car, but it ran Techstream. Yes, I almost drove off once without unplugging the 120 volt extension cord for the PC and monitor first. >_>

    I did try one of those "active" USB extender cables so I didn't have to schlep the computer around, but I couldn't get it to work with the OBDII-to-USB cable. It did work with some other stuff, like a thumb drive and a webcam - just not the OBDII cable.

    Now I run Techstream on an old Acer laptop that somebody gave me. It has Windows 8.1, 64-bit. There is an extra dance to do to get the 64-bit driver for the USB cable installed, but it works.

    I have never tried to run Techstream on Windows 10 or 11. If I had to use one of those, I'd probably try 10.

    Whatever OS you have, you will need Java. I used Java SE 6 on XP, and something newer (not sure exactly what) on 8.1. You can download old Java versions directly from Oracle after you make a free account.

    You also need a "Mini-VCI" OBDII-to-USB cable, which should be available on Amazon. I'm not aware of any Bluetooth adapters that work with Techstream.

    The post I made when I initially got it working is here: Attempting to get our original 01 Prius back on the road | PriusChat

    In general, @ChapmanF is right about P3125. I stopped counting at 70 sub-codes in the factory manual. Some of the sub-codes are as simple as a open circuit in one of the data buses to the inverter (mice chewing on wires?) and some are an immediate "replace inverter/converter assembly".

    You probably know this, but the inverter/converter is that big square box under the hood that says "Toyota Hybrid System" on top. In the absence of a more specific trouble code, it might be worthwhile to get a strong light and inspect the low-voltage harnesses coming out of it, as far as you can with everything installed, to see if there are any beat-up places, bare copper showing, etc.

    At least a few years ago, you could get PDFs of the factory manual from Toyota, for a price. The site was (is?) run by Snap-On; it offered a one or two-day subscription for like $10. Unfortunately, it comes as a couple of thousand individual PDFs, and at least back then, there was no "download all as ZIP" option. I can't remember if it was scraper-resistant or not; I do remember it took a couple of hours to get them all.
     
    #5 mroberds, Aug 24, 2024 at 9:18 PM
  6. ChapmanF

    ChapmanF Senior Member

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    Location:
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    Vehicle:
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    Model:
    IV
    The access options for the Toyota manuals are described on this page:

    Toyota Service Information and Where To Find It | PriusChat

    If you are signed in to the Technical Information Service, there is a whole lot of information there; not just the manuals, but service bulletins, quick technical guides, course materials for the Toyota technician trainings, and so on.

    A lot of those things are straight downloadable PDFs, but the manuals aren't (except the legacy ones for older models). They're just straight HTML web pages with images. You can click your browser's "Print to PDF" to save PDFs of the manuals, but that's a whole lot of clicking if you want to save a several-thousand-page manual.

    The online pages have a lot of cross-reference links. One procedure might say something like "Remove intake manifold [INFO]" and you can click the link to go to the manifold removal steps. After "Print to PDF" you end up with a bunch of blue [INFO] boxes that don't take you anywhere, so that's less convenient.

    The online wiring diagrams are nicely interactive: you can click on one component, say, and the circuit it's in gets highlighted and you can follow it around between different views, pull up the connector part numbers, and so on. It has download-PDF links, which end up giving you a different, PDF-formatted version that is essentially the same as how the old paper versions looked.

    The two-day subscription has not been $10 for a while now; as of today I think it's $25.
     
    #6 ChapmanF, Aug 26, 2024 at 3:58 PM
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