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P0b42 code

Discussion in 'Gen 3 Prius Technical Discussion' started by Szulkarn, Aug 18, 2021.

  1. Szulkarn

    Szulkarn Junior Member

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    Car check engine and check hybrid warning system came up.
    Use torque pro and it says maf sensor. But went to toyota dealer P0B42 code came up.
    The mechanic immediately without any further checking says new set of hybrid batteries.(cant just buy per piece. I asked to check each cells voltage and its all good. No suspicious under voltage.
    Did a quick search yhe code says either
    Faulty Battery smart unit or
    Faulty HV battery assembly
    If all 28 cells are good. Could it still be a faulty hv battery assembly?
     

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    #1 Szulkarn, Aug 18, 2021
  2. ChapmanF

    ChapmanF Senior Member

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    The code you have is a problem with the voltage sensing arrangements inside the battery, not a problem with the NiMH modules themselves.

    It can often be resolved by repairing the battery, not by replacing modules or replacing the battery.
     
    #2 ChapmanF, Aug 18, 2021
  3. rjparker

    rjparker Tu Humilde Sirviente

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    Dealers don't repair batteries.
     
    #3 rjparker, Aug 18, 2021
  4. ChapmanF

    ChapmanF Senior Member

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    ergo, dealers aren't the best place to go when battery repair is indicated.
     
    #4 ChapmanF, Aug 18, 2021
  5. Szulkarn

    Szulkarn Junior Member

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    Thank you for the reply. Im not sure how to repair the battery.
    So i should check each individual cell for a bad battery?
    What parameters counts as bad battery? Thank u again sir.
     
    #5 Szulkarn, Aug 18, 2021
  6. ChapmanF

    ChapmanF Senior Member

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    No, for this trouble code, don't bother testing the NiMH modules.

    People always worry about the NiMH modules in the battery going bad, and plan for it, and obsess over module voltages, and so on. Yes, it is true those modules deteriorate over time, and eventually they may need to be replaced.

    But this trouble code is not about that.

    The battery is built with a monitoring system that measures the module voltages (really, measures voltages in blocks of two modules each). Yes, the monitoring system is there to detect when the modules are going bad.

    But what happens if something goes wrong with the monitoring system?

    Then you get this code.

    So it is not telling you something about the modules being bad. It is telling you it can't tell you whether the modules are bad or not, because the monitoring system is broken.

    Solution: fix the broken monitoring system.

    That system involves a cheap bundle of wires (known as "wire, frame, no. 2") connected to a small computer inside the battery case. The wire bundle may be damaged, or its connection to the little computer, or maybe the little computer itself. By inspection, one can find what needs to be repaired or replaced.

    The repair is common; there are a lot of threads on PriusChat about it.
     
    #6 ChapmanF, Aug 18, 2021
    dig4dirt likes this.
  7. Szulkarn

    Szulkarn Junior Member

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    Thank u ill do some digging on the forum thank u for your detailed explaination. Maybe ill get back at yoy if i have further questions? Thanks.
     
    #7 Szulkarn, Aug 19, 2021
  8. Szulkarn

    Szulkarn Junior Member

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    Hi. The dealer took apart the casing and found corrosion on the battery terminals contacts, i asked to to unplug the cables going to the smart unit (battery ecu) found a little bit of mold in the cables.

    I was hopeful that this is the cause of the problem.

    They cleaned it up realgood. And reinstall the battery back to the car.
    Same dtc p0b42

    They insisted that the battery was bad need to be replaced.
    They said if the smart unit (battery ecu) was bad. Techstream wouldnt be able to live data log the each cell voltages. (Please verify)

    I took a snapshot of the voltages in techstream.

    Seems blok 1 and 2 its off by more than 0.03volt. But the numbers do fluctuate up and down. Sometimes goes up more than 0.03v , sometimes its less than 0.03v.

    Im trying not to bite the bullet to replace the whole block.
    Im currently in asia where hybrid cars are less common. So private workshops are hard to find.
    Is there a diy method where i could repair or recondition the batteries myself.
    What are the tools i need to use .any advice and help is appreciated

    Thank you sir
     

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    #8 Szulkarn, Aug 31, 2021
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