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Master Warning Light and Breaking System Light with P0A08

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Aaron331, Mar 11, 2015.

  1. Aaron331

    Aaron331 New Member

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    my 2006 prius has the Master warning light(red) and the braking system light (Yellow) on while I am driving, and I went to the dealer.

    The technician told me that he could not verify any warning lights ON at that moment, and he performed health and diagnostic checks on it. He inspected connection at auxiliary battery and junction box 1. All checked OK at this time. No repairs recommended at this time.

    However, the master warning light came on when I pick up the vehicle. The dealer told me that they will inspect it again tomorrow. And they found that there a P0A08 error code. They suggested me to replace the hybrid converter/inverter.. $4733 for NEW and $1672 for used...(DC) I dont know why the problem is seems not related to the lights....
    My car can still drive while the lights ON.

    I'm wondering what is the effect if the hybrid converter is bad/broken. Or what might cause the hybrid convertor code appear. Battery problem? Is it Ok to drive the car without that convertor or bad/broken convertor? Any Suggestion?
     
    #1 Aaron331, Mar 11, 2015
    Last edited: Mar 11, 2015
  2. TampaPrius.com

    TampaPrius.com Active Member

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    First check to see if the inverter pump is running by looking in thee inverter coolant reservoir while the car is in ready mode. There should be turbulence from coolant flow. If it is still the pump is bad.

    Inverters are not known for failing typically unless the car is driver w/o coolant flow or reverse polarity jump starting. If you need to replace inverter a used one can be found for around $100 here

    Search Results

    Installation at an independent shop should be no more than $300 + new coolant.
     
    #2 TampaPrius.com, Mar 11, 2015
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  3. Aaron331

    Aaron331 New Member

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    Thank you for your information.
     
    #3 Aaron331, Mar 11, 2015
  4. bisco

    bisco cookie crumbler

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    how many miles on her?
     
    #4 bisco, Mar 11, 2015
  5. Aaron331

    Aaron331 New Member

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    Around 201000 miles already
     
    #5 Aaron331, Mar 11, 2015
    Last edited: Mar 12, 2015
  6. Aaron331

    Aaron331 New Member

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    And I changed the aux battery and fuseable link about 6 months ago.
     
    #6 Aaron331, Mar 11, 2015
  7. nh7o

    nh7o Off grid since 1980

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    A blown fusible link would say that the 12V battery was jumped with reverse polarity. As pointed out, that is about the only thing that can take down the inverter, although there is not usually a time delay of 6 months. Please call the service department and get the list of codes that were read from your car, and list them here.
     
    #7 nh7o, Mar 11, 2015
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  8. Aaron331

    Aaron331 New Member

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    On 3/11/15, the dealer only states that they found code POA08 with info code 264 checked. They states that the vehicle needs a new inverter parts.

    I have some previous code:
    P0420, which is the Catalyst efficiency below threshold( I didn't fix this since I think this problem just make me not pass the smog test only, and my car wont need to do smog check until 2016)
    It is wired that they did not found this code when they inspect my Prius today. (3/11/15)

    What is the worst case if I leave do not replace the inverter, and I keep driving?
    Is it easy to replaced the inverter by DIY?
     
    #8 Aaron331, Mar 12, 2015
    Last edited: Mar 12, 2015
  9. nh7o

    nh7o Off grid since 1980

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    Here are the possible problem areas that are caused by that code:
    - Auxiliary (12V) battery
    - Fusible link block assembly
    - HV control ECU
    - Fuse (for 12 V electrical equipment)
    - Engine room relay block
    - Inverter cooling hose
    - Water pump with motor assembly
    - Cooling fan motor
    - No.2 cooling fan motor
    - Wire harness or connector
    - Inverter with converter assembly (DC /DC converter)

    You will note that replacing the inverter is the last item on the list. We have seen enough cases of dealerships swapping parts on suspicion only, and then finding that the problem was elsewhere. However, you still get charged for their error. I would want to make sure of all else before changing the inverter.The above tend to point to overheating of the 12V charging section (Converter) due to improper cooling system function, or failure of the 12V battery (shorted cell).
    Since we don't know what the fundamental cause of the error is, there is no way to say what the result of driving will be. You will not get regenerative braking as it now stands, which is not a good situation. You may completely drain the HV battery.

    It can be DIY, and there are instructions on this site and other places. You will need to get the relevant service manual sections from the Toyota website. (subscription). You will also need to get a mini VCI code reader to make sure the work has been done properly.
     
    #9 nh7o, Mar 12, 2015
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  10. Aaron331

    Aaron331 New Member

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    Thank you for the information, and I will try to check all those before I change the inverter.
     
    #10 Aaron331, Mar 12, 2015
  11. maverick1970

    maverick1970 Junior Member

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    Hi Aaron.

    What did you end up doing? I am experiencing a similar issue. Thanks!
     
    #11 maverick1970, Apr 13, 2015
  12. Aaron331

    Aaron331 New Member

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    I end up with doing nothing. When I arrived to Toyota and picked up my car, I talk to one of the technician. He told me my car does not have any breaking issues. It is the converter problem, and it cost 6000 for a new and 2000 for a used one. After I picked up my car, the master warning light is still on but not the breaking light. I considered to replace an used converter at other car repair shop. However, all the lights off on the next day. The lights off continue for like couple weeks.. So I just leave it. And Now, the master warning light is on, but I just drive it with the light on since my car is already have a very high mi.
     
    #12 Aaron331, Apr 13, 2015
  13. Aaron331

    Aaron331 New Member

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    As nh7o mentioned, there are many cases to cause this code appears... it might not be the converter issue.
     
    #13 Aaron331, Apr 13, 2015
    Last edited: Apr 13, 2015
  14. bisco

    bisco cookie crumbler

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    thanks for the update, all the best.(y)
     
    #14 bisco, Apr 13, 2015
  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I suggest that you make the Prius READY, then measure the voltage across the 12V battery using a digital multimeter. The voltage reading should be ~13.8V. If it is much lower, then the 12V battery will not be properly charged by the DC/DC converter which has failed. That is the significance of DTC P0A08.

    The worst case is that the 12V battery will be depleted and your car will stall along the side of the road. You will not be able to resume driving until you put a new 12V battery in. Then that battery will also be depleted after a short period because it is not being charged.

    I would not say it is "easy" to replace the inverter, but it is certainly possible if you can follow instructions, have prior automobile repair experience and a reasonable set of metric tools. Obtain repair manual info at techinfo.toyota.com
     
    #15 Patrick Wong, Apr 13, 2015
  16. Aaron331

    Aaron331 New Member

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    Thank you for the information. Last time I checked the 12 V battery is about a month ago, which after I picked up the car from toyota. On the multi-screen display, it reads ~13.9V. Does it mean that it is not a converter problem?
     
    #16 Aaron331, Apr 14, 2015
  17. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you can trust the voltage reading from the MFD, you would be correct that the DC/DC converter is OK. I suggest you verify that reading by using a decent digital multimeter, measuring across the 12V battery when the Prius is READY.

    How about the traction battery state of charge as reported by the MFD? What are the state of charge readings? Are they moving up and down?

    I also suggest that you obtain Mini VCI so that you can be self-sufficient with regards to reading the DTC logged by your car.
     
    #17 Patrick Wong, Apr 14, 2015
  18. maverick1970

    maverick1970 Junior Member

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    Hi Patrick.

    How would I check the traction battery state of charge as reported by the MFD?

    Thanks,
    Jeremy
     
    #18 maverick1970, Apr 14, 2015
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Look at how many bars appear on the traction battery state of charge gauge. Normally there will be 5 or 6 blue bars. The gauge may drop down to 1 or 2 pink bars when air conditioning is used in the summer and the car is stopped, and may rise up to 7 or 8 green bars when you are descending mountainous terrain at speed.

    If you see wild swings in the gauge over a short period of time, that is a leading indicator that the traction battery is about to have a problem.
     
    #19 Patrick Wong, Apr 14, 2015
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