P3191 error msg after auxiliary battery swap

Discussion in 'Gen 2 Prius Technical Discussion' started by cathcycler, Oct 23, 2008.

  1. cathcycler

    cathcycler Junior Member

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    I replaced my auxiliary battery using the Miata battery suggested here. My Prius runs great, but I get "dash fireworks" showing the check engine light. I checked the code and it was P3191. I erased the code, but it keeps reappearing.

    Any ideas?
     
  2. David Beale

    David Beale Senior Member

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    I searched on the internet and found a tech discussing this code. He found it was caused by an over-rich mixture (pools of fuel in the intake system), caused by a worn PCV valve (which he says is difficult to replace). In your case the over-rich mixture may have been caused by the low battery not letting the car run to get warm when you tried to start it.

    He said the solution is to replace the PCV valve and run the car enough to get it nice and warm. BTW, this recurring code is a known problem, but it appears there is no other solution for it.
     
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    DTC P3191 is "engine does not start". I suggest that you start by replacing the iridium spark plugs if they have not recently been changed, and clean the throttle body assembly. Also ensure that the engine oil level is correct (not overfilled) and 5W-30 viscosity is used.

    The PCV valve is located on the corner of the valve cover nearest the inverter and the firewall, and can be reached after the engine wire harness over the valve cover is removed sufficiently to provide clearance to the PCV valve. It should be changed after 60K miles.

    P3191 has nothing to do with the 12V auxiliary battery, so its appearance after you replaced the battery is coincidence only.

    Toyota issued TSB EG011-03 that advises replacing the engine ECU once basic tuneup issues have been resolved. Note the current part number of the engine ECU which is listed in the TSB; you may want to compare to the part number of the ECU installed in your car (the engine ECU is located behind the glove compartment.) You may be able to purchase a salvage ECU for a reasonable amount; make sure that the part number is correct.

    Another possible problem is that fuel line pressure is low due to a marginal fuel pump and/or circuit opening relay (aka fuel pump relay); this can be assessed by measuring the fuel line pressure per the TSB.
     
  4. ChapmanF

    ChapmanF Senior Member

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    About two-out-of-five times I have the aux battery disconnected, when I reconnect it I will get a stall-after-fifteen-seconds, exclamation points, and this code. After clearing the code with a generic scanner, everything is happy. Never happens again, or any other time, and I doubt, in my case at least, that it has any genuine mechanical cause. I suspect some intermittent bug in ECU initialization. I have seen other people post suspiciously-similar-looking reports.

    Now in this thread, the OP reports clearing the code and the problem recurs, which is very different from anything I've seen, so the OP's car probably has something else going on. But I've seen enough of the mystery-P3191-after-connecting-aux-battery reports to guess that in many cases there may be no need for concern unless it does recur.

    -Chap
     
  5. lid

    lid New Member

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    Just wanted to note that there is an updated TSB with better information.
     

    Attached Files:

  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    :confused:
    The file that you attached is TSB EG011-03 dated 6/12/2003, same as I earlier posted. If you have a recent update to that TSB, please post again.
     
  7. lid

    lid New Member

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    If you look at the revision notes, the last revision was in 2007. The contents are somewhat different too. When I first saw this I was confused too, since the two versions have the same date.
     
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