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Code P0A4B!

Discussion in 'Gen 2 Prius Main Forum' started by dasterndastern, Sep 10, 2017.

  1. dasterndastern

    dasterndastern Junior Member

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    Hi all... I have a code P0A4B situation, looked at a couple other threads already, gathered relevant info... but would appreciate any further insight folks might have...



    I have a 2009 Prius, 178,000 miles on it...

    Last Thursday, the car passed Massachusetts State Inspection, received its new sticker...

    Last Sunday, on a very very rainy afternoon, we took a drive an hour and a half south for lunch. No problems.

    On the way back from lunch, under a now-clear sky, we got about five minutes into our drive and got the red triangle - along with several other warning lights on the dashboard display. The little green car on the lcd Energy Monitor screen in the center of the dash also changed, to a car with a slash through it.

    The car kept driving fine.

    We pulled over. Consulted the manual - I should state here that I am not afraid of opening up the hood and tinkering, but I have zero expertise/knowledge to justify doing so - and after learning what the red triangle meant, decided we should call AAA, get the car towed to a service station, borrow another car to drive home with. So we did just that.

    It was a busy Sunday for AAA. They were going to be a long time. Everyone else left with friends to get the other car, I stayed behind with the Prius. And got to thinking about the inspection that had just been done. What if something had been knocked loose? It was worth opening the hood, anyway. So I did. I stared at the engine, etc, for about ten seconds and said to myself, who am I kidding, I have absolutely no idea what I'm doing here.

    So I shut the hood. And for the heck of it, started up the car again.

    All the warning lights were gone.

    I drove around for five minutes. No warning lights. We cancelled the AAA call. Drove home, on the highway, no problem. I drove around town, probably another 50 miles total, over the next couple days, no more warning light, except on one big bump the first day back, the cabin lights for some reason blinked quickly on and off. I decided to take the car in just to have it double-checked. Took it to our Toyota service center, LIA Toyota of Northampton, last Thursday.

    They could not get the red triangle to come on either. But they did read the code, as above. Here's what they said.

    Possible malfunction in transaxle (Motor/Generator #1 or #2) has code P0A4B (generator position sensor circuit) with detail code 253. Code is not pending. Malfunction is no longer present.

    Performed visual inspection of related wiring harness etc. No obvious problems.

    If code comes back on transaxle assembly will likely need replacement. $5582.92 for replacement.

    That .92 terrified me.

    No. But seriously.

    It would be insane to spend that kind of money on a repair, obviously. And even buying a reconditioned transaxle assembly as suggested above is probably not the way to go.

    But am I wrong to think that it could be something else - perhaps related to the electrical system? Again, any thoughts folks might have would be greatly appreciated...
     
  2. dasterndastern

    dasterndastern Junior Member

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    Just an update on this thread - have now driven the car another 400 miles - without a recurrence of a warning light of any kind. Is that relevant? Any thoughts appreciated... TIA.
     
  3. bisco

    bisco cookie crumbler

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    honestly, we'd just be guessing. loose connection, vermin, etc. have you tested the 12v?
     
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  4. dasterndastern

    dasterndastern Junior Member

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    <grin>

    Yeah. I get that - thanks for the guesses. I'm just thinking out loud myself here - thinking that if I go another few hundred miles with no recurrence, it's (relatively) safe to indulge my wishful thinking, i.e., that the code doesn't reflect an actual problem with the hybrid system but rather something more intermittent...

    Only one course of action, here, it seems to me.... wait and see!
     
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  5. SFO

    SFO Senior Member

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    If at a loss on what to do next..

    and assuming it hasn't already been changed in the last 50k, it's never too late to drain and refill the WS fluid in that transaxle.
     
  6. edthefox5

    edthefox5 Senior Member

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    That sensor connector with its wiring is mounted rather low on the trans and known to rot out if the suspension is really rusted and the bottom of the car has seen a lot of salty water. There's a few threads about it here but haven't heard about that sensor in a few years. I don't believe it's repairable without pulling the trans. It's referred to as the resolver.

    So of course my question to you what does the front chassis look like?
    Is it rusted all to hell?

    Also use the search forum button up top and search: Trans resolver

    There's also a YouTube that shows what it does and where that resolver external plug is mounted on the end of the trans on the drivers side. The plug tends to corrode and rot out given the right circumstances. I made sure mine was lubricated like most of my cars chassis.

    Youtube title is: Prius resolver
     
    #6 edthefox5, Sep 27, 2017
    Last edited: Sep 27, 2017
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  7. bisco

    bisco cookie crumbler

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  8. ws309

    ws309 Junior Member

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    I got code P0A4B also when I replaced the engine wire harness. I havent changed the trans oil yet. Ive looked at that sensor and it is a real nightmare to get to.
     
  9. SFO

    SFO Senior Member

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  10. ws309

    ws309 Junior Member

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    Thanks for getting back to me so fast. I replaced the engine with as jdm 2015 engine and in the process 3 sensor connectors were disconnected wrong.(wires got pulled out of the connectors) I looked up wire harnesses and found one for $150.00. I figured that would be the fastest and cheapest way to go. On paper it looked good but after installing the new harness I got the P0A4B code and here I am. It got late and dark and I'm in the street so I packed it in and will finish putting it all back together in the A/M. I cleaned the sensor and reconnected it and I'm hoping that will resolve the issue.