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Inverter Pump Replacement Nightmare

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bryce Paige, Sep 1, 2022.

  1. Bryce Paige

    Bryce Paige Junior Member

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    Hey everybody,

    About a month ago I decided it was a good time to drain and replace the coolant in my inverter cooling loop before a road trip I had later that week.

    Everything went fine at first until I went to purge my system of air. Putting my Prius into accessory mode (pressing the power button twice without foot on the brake) didn't cause the pump to activate at all and under no circumstances could I get it to push coolant. This was extremely confusing as I had no codes or previous issues with my car before draining the coolant.

    Because of this, I ended up overnighting an inverter pump from Autozone to install in my car before the road trip. This pump went in fine and I was able to hear it run as soon as I put my car in accessory mode and I was able to purge it of air quickly.

    Unfortunately, this is where the weird issues begin. About ~70 miles into my trip, my car kicks on the red triangle of death and kills my AC and cruise control. Using my code reader I was able to see that I was getting a P0A93 (Inverter Cooling System Performance) code and that my engine temps still seemed just fine.
    Being stranded in the middle of nowhere and still 100 miles from my destination, I decided to drive the rest of the way there after unplugging my 12v battery and letting the car rest for about 30 minutes.
    The code came back about 30 minutes into the rest of my drive and I decided to drive carefully the rest of the way and troubleshoot it once I was there.

    Just one exit from my destination my brake light suddenly came on and a constant beeping tone started coming from the dash. I quickly pulled onto the shoulder and lost complete power and my brake booster seemed to be nonfunctional. Luckily I was able to get off the road safely but that experience made me realize that I need to solve whatever weird issue this is. Unfortunately, its inconsistency in occurring has made it very hard to pinpoint the problem.

    After that issue, I restarted my car and drove the final few miles home on surface streets. I put in my original pump and drove it home the following night with no issues.

    Today I took my first road trip in several weeks and had the dreaded code come back onto my dash about 100 miles away from my house. I ended up resetting the car several times but the code kept coming back within 20 miles or so of starting my car. This was accompanied by engine surging, lack of cruise control, and AC.

    The codes that accompanied the P0A93 main code were inconsistent but had never occurred before. I'll list them below.
    p0136 (Oxygen Sensor Circuit Bank 1 Sensor 2)
    p0011 (Intake Camshaft Position Timing Over Advanced)

    At this point, I am ready to buy another inverter pump and install it but I am wary of throwing money at this problem I've created just by attempting to do so maintenance.

    Did I somehow damage the pump when I flushed it?
    Is there a chance it wasn't running before? If so why is it kicking out codes now?
    Is there any reason why the new Autozone pump would cause codes to be kicked out when it seems to be running in better fashion than my original pump?

    Any help on this matter would be greatly appreciated. I want to get my car back into good shape and this issue has been going on for far too long.

    Thank you!
     
  2. bisco

    bisco cookie crumbler

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    checking the reservoir will tell you if the pump is working. i don't think engine temps are controlled by the inverter cooling loop.
    check your 12v battery health with a free load test at an auto parts store.
     
  3. ChapmanF

    ChapmanF Senior Member

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    A bit of terminology to help people trying to read your post: the mode you selected (button twice without brake) is called "ON". "ACC" mode is button once without brake. "READY" mode is button once, with brake (when you see the word READY on the dash).

    Other than the terminology, you did have the right mode; the cooling pump should run in ON mode.

    Because of this, I ended up overnighting an inverter pump from Autozone to install in my car before the road trip. This pump went in fine and I was able to hear it run as soon as I put my car in accessory mode and I was able to purge it of air quickly.

    There's a good chance that the DC/DC converter (part of the inverter assembly) shut down protectively because of the overheating. With the converter shut down, nothing was charging the 12 volt battery as you continued to drive, and when that voltage became low enough to pose problems powering the brake system, then you had brake issues.

    I would focus on getting the overheating issue resolved and making sure the 12 volt battery is well recharged, and then see if any of those other issues recur at all.

    Aftermarket inverter cooling pumps don't seem to have a great reputation here on PriusChat.
     
  4. Bryce Paige

    Bryce Paige Junior Member

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    Thank you very much for your reply! I have gone ahead and ordered an AISIN branded pump to install once I get my car home. Hopefully this is the proper OEM replacement as I have seen it posted elsewhere.

    I will unfortunately still have to drive my car quite a distance to get it home but I plan on doing this in the dead of night to avoid as much heat as possible. On top of this, I will be installing another generic cheapo Amazon inverter pump while I am down here so that I know at least I have a pump that is running. Even if it causes codes to be kicked out regardless.

    I hope the OEM branded inverter pump will get rid of all of these issues once I get home early next week, but the fact that none of these issues were occurring before I drained the OEM pump still confuses me...

    Did I either manage to kill my inverter pump myself by just changing the coolant in it or did I just coincidentally stumble across it as it was failing? Either one seems highly improbable and has me worried that replacing just the pump won't be the end of these issues...
     
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    When you refilled the inverter cooling system, did you use the bleeder fitting just in front of the inverter to purge air? A system with air in it is fairly noisy (whine-hum) when the pump runs. When the air is bled the pump is barely audible (but there are ripples in the coolant tank)

    I put a 3 foot long piece of 1/4" hose (I like clear hose) on the bleeder. Turn the car ON and hold the free end of the hose in the inverter tank while opening the bleeder screw. It can take 5 minutes (or more) of running before all the air is pushed out of the cooling loop.

    Your problems are likely caused by the pump (or air preventing the pump from pumping), but it can also be something wrong with the radiator or hoses.

    Posted via the PriusChat mobile app.
     
  6. pasadena_commut

    pasadena_commut Senior Member

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    The hose doesn't have to be completely clear, but it must be clear enough to see if there are bubbles moving in the tube.