2006 Prius HV Battery full, limp mode, DIY help

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by titan_prius, Feb 9, 2023.

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  1. titan_prius

    titan_prius New Member

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    I recently took out the battery of my 2006 Prius (170k miles). Before, my battery was draining very quickly. When idling the battery would almost rapidly drop to purple and the ICE would come on, which seems to be a common issue with battery age. It would charge back up just fine. I have a mini VCI and TechStream and found I had intermittent P0A80 (screenshot 1). Eventually the car went into limp mode a few times, and I decided to band aid fix until I could afford a new battery.

    I replaced some weak modules(after sitting outside the car for about a week. All measured between 7.6-7.4, except for 4 outliers below 7.3), and after driving the car for about a week it seemed my problem had been solved. The battery could hold a charge much longer and my mpg improved. Idling did not cause the battery to immediately drain. It drove fine for about a week.

    Then I got some warning lights, techstream read P3017 (battery block 7 becomes weak), P3021 (battery block 11 becomes weak) and the battery fan in the back of the car would blow max speed constantly. I cleared the code a few times (fan turned off) and drove for a few days in between. It became more frequent and eventually engine would rev up and the car would go into limp mode again.

    I opened up the battery again and this time I replaced modules in block 7 and 11, and charged each module to 8.3 volts before putting it back in. Now, almost immediately, warning lights appear and I get P3019 (battery block 9 becomes weak), and max speed battery fan. And almost immediately afterwards the car goes into limp mode. In TechStream's freezeframe (screenshot 2), even though it lists block 9 as weak, block 9 is the highest value in the screenshot. Also, the battery temperatures in the screenshot don't seem high enough for the fans to blow max speed. It is the middle of winter here in Virginia.

    I know the MFD is not a proper source for a diagnosis, but it shows some interesting behavior. The battery holds an almost full charge, but is only used (yellow arrow to the wheels) when moving very slowly. When accelerating or driving above 10 mph, the engine takes control and also charges the battery. The battery powers the wheels for only a split second before the battery starts being charged by the engine. I can't find any other examples with this behavior, as most people experiencing this issue have almost empty batteries when the car relies on the engine. However, mine is almost full and is not participating. Even in TechStream it shows that the battery state of charge is 50%+.

    I think I made a mistake when putting the battery back in. I haven't put the trunk or walls back in, because I expected I might need to remove them again soon. I followed these two videos:


    If anyone has experienced something similar I would appreciate the help. Also if anyone knows what in screenshot 2, "Batt Pack Current Val" means, and why it is negative. In all the TechStream screenshots I have seen it is always positive. Sorry for the essay but I can provide more info if needed. Thanks.
     

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    #1 titan_prius, Feb 9, 2023
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    That parameter is a measurement of the electrical current (amps) discharging from the HV battery (positive value) or entering the HV battery (charging, negative value).

    So, in your first photo, the HV battery is at a 7.98 amp discharge. Your TS screenshot is showing you have a problem with blocks 11 and 12.

    In the second photo, the HV battery is undergoing a 17.24 amp charge and your TS screenshot is showing a problem with block 9.

    One of the first things I would do, since you've already disassembled the battery, would be to verify all my fastener torques. All those 8mm hex head nuts need to be torqued to 48 inch-lb. (INCH-LBS not ft-lbs). Too many DIYers cause their own heartache by not properly torquing these fasteners.

    Make sure you're counting modules correctly. Block 1 module 1 on a Gen 2 is the module furthest from the ECU. Module #1 on a Toyota is always the module that has the heavy orange cable connected to the (-) terminal.
     
    #2 TMR-JWAP, Feb 10, 2023
    Last edited: Feb 10, 2023
    Bryan R likes this.
  3. Bryan R

    Bryan R Junior Member

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    I’m actually having a similar issue, my car was giving me electrical issues with communication code U0293 that started me on the path of changing my HV ECU, mistakenly my ECM, and eventually seeing pin 22 on my battery ecu corroded. I decided to finally look into the hybrid battery myself literally last week, and found my battery harness and bus bars badly corroded specifically on the negative terminal that connects to module #1 which is also linked with the battery ecu wire that goes to pin 22. This wire too was corroded. I end up buying a used and very good condition battery harness and battery ecu. I cleaned all the terminals with whatever carbon residue on the battery each module terminal in prep for the new bus bars and harness, on the positive side of the battery modules I cleaned the bus bars of corrosion and with 2500 grit paper polished the nickel plated bus bars from the black carbon buildup.

    7 days later this past Sunday, I finally got my car to start programmed everything with the 30 minute flashing, and drove my car for about 20 minutes and the red triangle and all lights came on with the battery fan continuously blowing.

    I’ve been deciding on what to do now as my obd scanner doesn’t pick up what codes are there. I left the car over night yesterday and decided to drive to see what would happen my car seemed to be driving better than ever with my mpg going high and battery levels to be very stable exactly as OP is saying! About 30 minutes “problem” on MFD, red light triangle and etc lights, battery fan on like crazy!

    I’m thinking of driving on limp to my Toyota dealer just to get the accurate codes and know where I go from here. I read people saying it’s a bad battery, or the inverter cooler pump, maybe thermostat. Ive even checked the fuses particularly the am2 fuse and switched it out to see if that would make a difference, I check the coolant reservoir and saw turbulence and felt the rubber hose from the inverter to the pump and felt vibration and activity like the pump is working. But if this any of these are the case why the hell is it happening after removing my hv battery?
     
    #3 Bryan R, Oct 8, 2024
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    At this point, you need to be able to scan the HV battery ecu and the hybrid vehicle control ecu.

    Here's a thread that reviews several scantool apps and devices for smartphones. Some are capable of scanning all systems on a Gen2 Prius. Something like Dr Prius is fairly limited but handy for checking HV battery block voltage readings.
    (FYI the Autel AP200 has been mostly replaced by the AP2500(or AP2500E)).
    https://priuschat.com/index.php?posts/3290690

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Oct 8, 2024
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  5. Bryan R

    Bryan R Junior Member

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    Check it out here are the codes I got from the dealer:
     

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    #5 Bryan R, Oct 9, 2024
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    The HV battery ecu has P3020. A code like that usually indicates a failed battery. The battery has 28 sealed modules that are monitored in pairs. So the ecu can see voltage for each of the 14 pairs (called blocks).

    If any one of the blocks is "too different" from the rest for "too long" a time, then the ecu sets codes. P30xx for a specific "block becomes weak", or P0A80 for "replace HV battery" (I would expect that code to be present).

    It MIGHT be possible (but unlikely) that there is a problem with the block voltage sense wiring or ecu. Again, you would need some type of scantool to look at block voltages. I would not be surprised if you do need a new HV battery.

    Posted via the PriusChat mobile app.
     
    #6 mr_guy_mann, Oct 11, 2024
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