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Dreaded "P Lock Malfunction"

Discussion in 'Gen 2 Prius Technical Discussion' started by stoshzack, Aug 13, 2020.

  1. stoshzack

    stoshzack New Member

    Joined:
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    Location:
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    Vehicle:
    2008 Prius
    Model:
    Two
    Hi All -

    I was working on our baby sitter's 2008 Prius. She asked me to replace the A/C blower motor as it was intermittent. I replaced the motor, and when she went to start the car, she got the dreaded "P Lock Malfunction". It will not shift into gear. I notice the transmission module under the glove compartment. Wondering if I did something to it during the blower install?

    I researched the forum for possible causes, and did the following.

    1) Battery - pulled the battery and took it to O'Reilys. It is a Toyota battery and only 3.5 years old. They said it tested good and they quick charged it. Put it back in and read the voltage on the dash info. Reading was 11.7 volts.

    2) Pull and replaced the P Lock fuse (i.e. brown 7.5 amp) in the fuse box.

    3) Cleaned the connector to the transmission module with electrical cleaner.

    None of these have worked. I still get the P Lock error and it will not shift into gear. Any suggestions on how to proceed?
     
  2. Prius_Cub

    Prius_Cub Member

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    Location:
    Radford, VA
    Vehicle:
    2008 Prius
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    II
    11.7 volts is low enough to cause issues and is most likely why the P-Lock message is displaying. That's what my '08 did when my last 12 volt battery failed a couple of winters ago.

    If you're able to put it on a charger for a longer period of time, do so and see if it charges to above 12.3-12.4 volts. If not...that battery might actually be bad. You can also jump it off another vehicle, just be careful about polarity when connecting it to avoid blowing any fuses or worse.
     
    stoshzack likes this.
  3. stoshzack

    stoshzack New Member

    Joined:
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    Location:
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    Vehicle:
    2008 Prius
    Model:
    Two
    Thanks for the response @Prius_Cub - tried a new battery, but that did not work. It was worth a try.
     
  4. stoshzack

    stoshzack New Member

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    Location:
    Wake Forest, NC
    Vehicle:
    2008 Prius
    Model:
    Two
    Took it to Toyota. They diagnosed it as a bad transmission control module. They want $1200 to install a new one. Anyone know if you can simply swap transmission control modules (i.e. replace with a used one), or do they need to be programmed?
     
  5. stoshzack

    stoshzack New Member

    Joined:
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    Location:
    Wake Forest, NC
    Vehicle:
    2008 Prius
    Model:
    Two
    Just an update. I called my Toyota dealership and asked if I could put in a used transmission control module. They said that I could (which surprised me), but that there would be a $150 "calibration" charge. I went and picked up two used transmission control modules from a local pick-your-parts place. Took them over to the dealership and it worked. $185 out the door which is much better than $1200. I am not sure every Toyota dealership would be willing to work like this. It was Fred Anderson Toyota in Raleigh. I was impressed with the service rep. Problem resolved.
     
    bisco and donbright like this.
  6. bisco

    bisco cookie crumbler

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    congrats, well done!