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P3120 with 235

Discussion in 'Generation 1 Prius Discussion' started by WHCSC, Jan 19, 2018.

  1. WHCSC

    WHCSC Member

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    This code points to the System main relay. Could this come from the service plug not being all the way locked? I haven't checked so I don't know if this is the case.
    If the relay needs to be changed per the service manual is this a DIY job?
    Any other suggestions of what to look at?
    Thanks
     
    #1 WHCSC, Jan 19, 2018
  2. ChapmanF

    ChapmanF Senior Member

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    3120 / 235 refers to a large loss of strength of the permanent magnets in the rotor of MG2.

    If it means what it says, replacement of the transaxle is indicated.

    However, before going there for sure, there are two things to rule out. First, if there are any DTCs from the battery ECU, those should be attended to first. Second, based on a repeat test with ignition ON, the manual may suggest replacing the SMR first. It doesn't explain (at least not in my 2001 edition) exactly how an SMR problem might contribute to an MG2 magnetism code, but those are the steps.

    I'd recommend looking up the 2003 manual, which might have made the troubleshooting procedure clearer. I'm almost wondering if there could be a typo in mine, somewhere in the part of the flowchart around the SMR.

    -Chap
     
    #2 ChapmanF, Jan 19, 2018
  3. WHCSC

    WHCSC Member

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    The one with the code is a 2002 and I have the manuals. There are no other codes so it says to replace the system main relay. Yesterday I cleared the codes and they didn't come up when I started the car or even after I drove it around the block.
     
    #3 WHCSC, Jan 19, 2018
  4. ChapmanF

    ChapmanF Senior Member

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    I suppose the unexplained interaction could be something like, an intermittent poor contact condition in the SMR could lead to less current flowing to/from MG2 than expected, triggering a code for a decrease in rotor magnetism, except a real decrease in rotor magnetism would be permanent and always showing up.

    May as well follow the steps, change the SMR and see what happens. Had the code been coming up often?

    It can be a DIY job for roughly the same DIYers who would consider HV battery rebuilding a DIY job (only less work). Class 0 or 00 gloves, inch-pound torque wrench, insulated tools, meticulous work habits....

    -Chap
     
    #4 ChapmanF, Jan 19, 2018
  5. WHCSC

    WHCSC Member

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    Thanks for the help!
    This is the first time the cade came up. My daughter parked in a friends driveway, turned it off, and when she came back out the lights came on. Maybe going into the driveway to fast, hitting the bump too hard could have jogged something loose?
     
    #5 WHCSC, Jan 19, 2018
  6. ChapmanF

    ChapmanF Senior Member

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    If it doesn't recur at least once, I might be inclined to solve it by doing nothing....

    -Chap
     
    #6 ChapmanF, Jan 19, 2018
  7. WHCSC

    WHCSC Member

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    I just went to get it and drove it 8.5 miles home with no issues. We even stopped to fill it up and nothing happened. Parked it outside and washed it, went to pull it in and got the lights again and same codes. Weird.
     
    #7 WHCSC, Jan 20, 2018
  8. WHCSC

    WHCSC Member

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    I'm not sure if these things can just work themselves out, but after driving it to and from work today all is clear.
     
    #8 WHCSC, Jan 25, 2018
    Raytheeagle likes this.
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