Red triangle and yellow exclamation DTC PoA08-264 and POA09-591

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by printone2, Dec 28, 2018.

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  1. printone2

    printone2 New Member

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    I have an 07 with 150,000 miles that throws these codes when it is raining. It can go a thousand miles without a problem if the weather is dry. I have replaced the inverter pump and fluid and also the 12 volt battery with oem parts. I have a normal turbulence in the inverter reservoir. I have inspected the rear hatch and surrounding body for gaps that might cause leaking but cannot find any and there is no water in the back of the car.
    Techstream shows battery (+B) at 13.76 volts on the POA08-264 DC-DC Converter status error and 11.17 volts on the POA09-591 error. I suspect the 11.7 volts is the cause of the Converter status circuit low input error (...591).
    I have noticed if I drive for about 30 minutes I can stop the car and restart it four times and the codes will stop and I am fine to continue driving without any errors. I am not sure if the car is warming up enough to cause the inverter connections to expand and make better contact or if it gets warm enough to dry out any moisture that is grounding out the connection. I also noticed that the error beep can reoccur if I am driving on rough pavement and it is raining.
    This leads me to believe I have a loose connection somewhere.
    Since I replaced the 12 volt battery I see readings from the MFD diagnostics in the 12.3 to 12.9 volt range with ignition only. When I push on the brake and turn it on while still in diagnostics I get either a 14.1volt ready which throws the errors or a reading of 15.3 volts. This makes me suspect that I am losing about 1.2 volts to some ground or
    Connection problem.
    The dealer wanted to replace the inverter for $5800 but know there are other things to try first before I look for a used inverter and some help.
    Question, what should the inverter B+ readings be In normal operation? Any thought on what would solve my connection or moisture problem? Car runs normally and traction battery stays normal with 6 or 7 bars SOC.
    Thanks. Stan
     
  2. JC91006

    JC91006 Senior Member

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    Used inverters are really cheap, maybe you should just go and install one. I sold one for $100
     
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  3. printone2

    printone2 New Member

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    Thank you. I can’t find the HV ECU? Any help?
     
  4. printone2

    printone2 New Member

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    More specifically, the HV Control ECU. I have looked them up on eBay so I know the shape but I thought it was under the passenger side glove compartment area under the carpet. That ECU did not look like the one I was looking for.
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The 2G Prius hybrid vehicle ECU is behind the glove compartment. It is next to, and to the left of, the engine ECU.

    The Classic Prius had the hybrid vehicle ECU under the carpet.

    I would say there is a low probability that a failed HV ECU is responsible for the two DTC that you had listed. It is much more likely that the inverter has an intermittent connection.

    Look for the wiring harness connected to the inverter, and find the wires which lead to body ground. Check the integrity of those connections to ground.
     
    #6 Patrick Wong, Dec 29, 2018
    Last edited: Dec 29, 2018
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  6. printone2

    printone2 New Member

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    Thanks Patrick. I have been reading your comments for several years. I took the cowl and wiper tray out to get some better access but could not get the c5 connection apart. Plan b was to see if I could get down to the body ground straps that are on the side of the drivers side strut tower. There are two bolts there that appear to have some corrosion around them. Even with the wipers and cowl removed I could not get down to the ground connections to clean them. I tried several different wrenches and sockets but counld not get enough room to break them free to clean them. Do I just need to pull the inverter to get to them?

    Is it likely that these ground connections are my problem?

    It has been dry but cold and the car never throws the error codes on days like these but I do measure 15.3 volts from the MFD when in the ready mode and when it gets wet the voltage drops down to 14.2 and up come the error codes.
    Thanks.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. The voltage measurements that you cite are very strange. It would be better for you to use a decent digital multimeter, and measure voltage across the 12V battery positive terminal to body ground. Also check the tightness of the 12V battery cable connections while you are back there, especially the negative cable where it bolts to the body.

    2. 15.3V is way above what the 12V bus should ever be at. Usually the most it will be is around 14V when the Prius is READY, and typically it is only 13.8V.

    3. A potential reason for the voltage being above the normal specification would be a poor ground connection from the inverter to body ground. The DC/DC converter voltage regulation circuit is mostly within the inverter. However the voltage regulation receives an input directly from the 12V battery. If the inverter has a poor ground connection that could cause strange voltage regulation outcomes.

    4. It doesn't take much resistance to develop a difference of 1.1V. Suppose the DC/DC converter is producing 30A current. Based upon Ohm's law (voltage = current * resistance), 1.1V = 30A * resistance. If you solve that equation, you will see that a resistance of 0.037 ohm is sufficient to cause that voltage drop.

    5. Hence, my suggestion that you need to inspect the grounding from the inverter to the body and also make sure the 12V battery connections are perfect.

    6. If it is not easy for you to access the existing inverter ground connections, maybe try running a supplemental grounding strap from the inverter body to a clean unpainted and not rusty part of the body. For example, one of the top strut mount nuts. This grounding strap will need to be very thick and robust since you are trying to improve upon the 0.037 ohm resistance. One possibility is copper wire braid intended specifically for grounding purposes.

    Good luck.
     
    #8 Patrick Wong, Jan 5, 2019
    Last edited: Jan 5, 2019
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  8. printone2

    printone2 New Member

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    Patrick,
    I did glove up and disconnect the orange leads from the inverter back to the traction battery after disconnecting the 12v negative battery terminal and the orange safety plug on the the traction battery. This was what was keeping me from getting to the strut tower body grounds. I cleaned them as best as I could but it did not seem to make any improvement. I did all this before I saw your last message but am only now able to send this message.
    Let me clarify that I have never read voltage readings on the 12 volt circuit on my ohm meter higher than about 13v. The 14.2 and 15.3 readings were from the MFD in DIAGNOSTIC mode.

    I did just get back from a couple of 150 mile trips. The one yesterday after cleaning my body grounds was terrible with error beeps several times a mile. The one today also started like that for about 2 hours. The MFD would show the battery icon on and off every few miles so it appeared that the battery was just moving back and forth across some threshold. Then I stopped for an hour and when I next started the car I did not get any beeps for the next hour home.
    The MFD was again showing voltages around15.3v. When I stopped the car about 30 miles from home I was able to restart the car three times and clear the errors (TOD and yellow “(!)”) and drove on with out any errors on the display or beeps.
    When I got home. I did measure from the positive of the 12 v battery to negative body ground and read 12.95v. Again it was a warmer dry day but yesterday was also dry and warm. Yesterday was atypical. I can’t explain. It does seem that my new 12v battery is getting drained overnight.

    I did find that my body ground on my previous battery was loose when I changed to the new one. I am sure I drove it that way for several months. Not sure if that is relevant. I replaced a tail light bulb during the trip today and about a month ago a headlight bulb burned out and I noticed that the headlight wiring has gotten hot and was not in great shape. I do not know if that would make any difference. I have not tried to replace the headlight wiring since the new bulb works.

    Next chance I get I will tear down to the c5 connection. I did get it apart yesterday but my Meter battery was low and I did not trust the reading.

    On your suggestion on improving the inverter ground strap. Would just attaching anywhere on the inverter and then to the strut tower bolts accomplish the goal? I will look for some braided copper to do that.
    Thanks. I am grateful and am learning a great deal and constantly reminded how much there still is to learn.
    Stan
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Assuming that you have a decent multimeter whose readings you can rely upon, I suggest you bring that along in the car. Next time you see the MFD display is 15.3V, immediately get out the meter and measure voltages at three places that are easily accessible to you:

    1. 12V battery positive terminal to body ground
    2. Dedicated positive jumpstart terminal in main relay/fuse box to body ground
    3. Passenger cabin 12V auxiliary socket, center of socket (which is positive) to surrounding shell (which is negative). Don't cause a short circuit while doing the measurement.

    Let's see what the variation is across those three readings, and that will help to determine if the MFD reading is real or bogus.

    Regarding the inverter supplemental grounding strap, my idea would be to find an existing bolt that goes into the cast aluminum inverter body as an anchor point. The grounding strap should be as short and as thick as possible.
     
  10. printone2

    printone2 New Member

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    Patrick
    I have been busy fixing my water pump this week and it continued to leak some due to some bit of dirt that got lodge onto the gasket of the new water pump. That seems to be almost repaired but there is a small bit of sepage around the gasket. This may have caused the many error beeps last weekend. I will have to borrow the scanner to see if there are other codes related to the coolant. I can see that I was losing coolant probably from the radiator cap being loose and the serpentine belt throwing it on that side of the engine and wiring connections. I had the water pump on hand so I just replaced it.

    Now back to your last post. The car does not have error light when I have about 15.3 volts of current on the 12 volt rail in ready mode.

    My meter is not anything special but I am seeing the MFD show 15.3 volts and can also see about 15.2x at the battery positive post to the body ground and same from the cigarette lighter below the glove compartment and at the fuse box next to the inverter jump point to body ground on the screw that attaches the fuse box to the strut tower.

    To create a better body ground I purchased a 10 gauge set of jumper cables from Harbor F. and some copper compression lugs 4/6 gauge. I stripped back a section of the jumper cable and folded it over and inserted in the copper lugs and crimped with a heavy duty coax crimper. This wire is stranded and has a reasonable jacket since I couldn’t find anything braided in copper. This extra ground wire is secured to one of the inverter perimeter 10mm top bolts and also to the bolt that secures the fuse box to the strut tower. The length is about 12 inches.

    When I turned the car back on I am still getting 15.3 volts on the MFD and also on the battery to body ground. The weather is bad and I have to put some splash guards back in place before I drive in these snowy conditions. I can’t see that that I have corrected anything. But will do some driving tomorrow. I am trying to find a way to freshen the body threads. I did not strip off the paint on my grounds and am just depending on the surface area of the bolt threads to make contact. I did not clean the threads to a bright finish just a wire brush. I did get tone for continuity on the new ground. Do I need to get more aggressive with my grounding surfaces cleanup?
    Thanks
    Stan
     
  11. JC91006

    JC91006 Senior Member

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    Regarding the errors you see that might be related to coolant seepage, you should check your radiator level (by removing radiator cap) I think you need coolant or you'll need to bleed the air out.
     
  12. printone2

    printone2 New Member

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    I went ahead and drained the radiator and added back about 1.5 gallons of SLLC through the radiator cap. I may not be done burping it yet but am aware of the some of the effort required to get the air out.
    Thanks.
     
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Stan,

    It sounds like your voltage reading of 15.3V is correct since the MFD reading is confirmed by your multimeter measurements. I would forget about trying to supplement the inverter grounding at this point, and instead recommend replacing the inverter with a used unit.

    That very high voltage reading (15.3V) is not good for the various ECUs and other electronics and potentially will shorten the useful service life of those components.
     
  14. JC91006

    JC91006 Senior Member

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    You should check the coolant level every morning (if you drove it the day before) for 3 days, add as needed.
     
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  15. printone2

    printone2 New Member

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    4D62F104-67B2-4B78-8295-17E47D5B0037.jpeg 4D62F104-67B2-4B78-8295-17E47D5B0037.jpeg
    Patrick,

    I expect to get a used converter in a couple of days. I did get copies of the P112 Hybrid control system manual. One of the testing steps #5 for a P0A08-264 is to check the fusible link block assembly. It says that F15-1 to body ground should test below 1 ohm and the same for F16-2. They both test open. When I test the 100a dc / dc-s fuse it tests for about .001 ohms or less using the lowest resistance setting (diode setting) which was how I tested the F15 and F16. Would the car run at all with the fusible link block showing opens on those two connections?

    The fuses do not look burnt or broken in any way. I don’t test ohms that often but could not get any tone for continuity on those two connectors either. Which I think confirms that they are open.

    Could the fusible link be my problem?

    I also have ground away the paint in the aux. battery body ground to improve the contact surfaces.
     
  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Just so that we are on the same page, this fusible link block assembly is the assembly that attaches to the 12V battery positive terminal, right?

    If so, it makes no sense that either F15 or F16 would have a connection to body ground. F16 is the 12V sense wire and F15 is part of the 12V bus which connects the 12V battery to the 100A DC/DC fusible link. Measure resistance from the 12V battery positive terminal connector on that fusible link block, to F15 and F16. You should get very close to 0 ohms.

    Also, the DC/DC-S fuse is 5A, not 100A. That is a fuse in the 12V sense line, and another typo in the repair manual. The DC/DC fusible link is 100A but that is located in the main relay/fuse box next to the inverter. There is a 120A MAIN fusible link within the fusible link block assembly.
     
    #17 Patrick Wong, Jan 13, 2019
    Last edited: Jan 13, 2019
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  17. printone2

    printone2 New Member

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    Patrick

    Yes,I am talking about the package that sets between the aux. positive and negative battery posts. Yes, I can verify that the reading from those two connections to the POSITIVE battery post approaches 0. So much for reading the manual literally. You hit a home run again.
    Thanks.
     
  18. printone2

    printone2 New Member

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    Where are videos of gen 2 inverter replacements? I see some for gen 3s but not gen2s.
     
  19. SFO

    SFO Senior Member

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    Try asking @NutzAboutBolts nicely :whistle:
     
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