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2002 Prius steering torque sensor calibration

Discussion in 'Generation 1 Prius Discussion' started by Q*bertZ, Oct 23, 2022.

  1. Q*bertZ

    Q*bertZ Member

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    20221021_113221.jpg 20221021_113304.jpg 20221021_113340.jpg 20221021_113821.jpg
     
    #1 Q*bertZ, Oct 23, 2022
  2. Q*bertZ

    Q*bertZ Member

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    My 2002 Prius needs the steering torque calibrated. My scan tool is supposed to do it, but fails. Are there pins on the OBD port I can touch together the magic number of times in the right number of seconds to set it?
     
    #2 Q*bertZ, Oct 23, 2022
  3. ChapmanF

    ChapmanF Senior Member

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    It only wants to learn the torque zero if it is not already learned, so there should be a C1515 code saying the torque learning is undone.

    If there is a C1515 (and no other codes), then all you need is to do the calibration. Stop on level ground, wheels straight ahead, no one touching the steering wheel. Jumper the Ts (*) and CG terminals (note Ts, not the Tc terminal that's familiarly used for code blinking and so on). Turn the key ON (without touching the steering wheel). Turn the key back OFF (without touching the steering wheel). The zero point should now be learned.

    However, if you have a previous zero point learned, or incompletely learned, you need the initialization step first, to forget the old value. Connect both Ts (*) and Tc to CG, and turn the key ON, then break/make the Tc connection 20 times within 20 seconds. Turn the key OFF. When you check the codes again, there should be only C1515, and then you can do the calibration as described earlier.

    It might be helpful to tell a little more of the earlier part of your story. How did you end up needing the steering torque calibrated?

    (*) BEWARE that Toyota moved the Ts terminal between Gen 1 and Gen 2. You might find a lot of references saying Ts is pin 12, which is right for Gen 2 or Gen 3, but not for Gen 1. In Gen 1, Ts is pin 14.
     
    #3 ChapmanF, Oct 23, 2022
  4. Q*bertZ

    Q*bertZ Member

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    Turn the key ON, but not READY. correct?
     
    #4 Q*bertZ, Oct 23, 2022
  5. ChapmanF

    ChapmanF Senior Member

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    Correct.
     
    #5 ChapmanF, Oct 23, 2022
  6. Q*bertZ

    Q*bertZ Member

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    This is the difference between gen1 20221023_184009.jpg
    and gen 2

    20221023_183733.jpg

    I'm going to try it. Maybe my code reader doesn't know about the pin difference.
     
    #6 Q*bertZ, Oct 24, 2022
  7. Q*bertZ

    Q*bertZ Member

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    I did it wrong.
     
    #7 Q*bertZ, Oct 24, 2022
  8. Q*bertZ

    Q*bertZ Member

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    Ooops, I was supposed to only break the TC connection. I was so fixed on that TS connection. The TS connection stays connected to the CG. Only the TC connection signals the 20 breaks?
     
    #8 Q*bertZ, Oct 24, 2022
    Last edited: Oct 24, 2022
  9. Q*bertZ

    Q*bertZ Member

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    Did not work. Could something be broken in my torque sensor?


    To clear the 1516 code (per the instructions) I put a paper clip between 4(CG) and 14(TS) and put a paper clip in 13(TC). 20221024_120807.jpg Holding the TC paper clip to the 4 and 14 paper clip, I turned the car on. Then, within 20 seconds disconnected the touching TC paper clip and reconnected it 20 times. Then turned the car off. Removed the TC paper clip and left the paper clip in CG/TS. I then turned the car on for 30 seconds(that was the timer value on my OBDII scanner, also noticed the ABS light was flashing) and turned the car off. Removed the jumper. Turned the car back on. Still no power steering.
     
    #9 Q*bertZ, Oct 24, 2022
  10. Q*bertZ

    Q*bertZ Member

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    I started the thread that my 2002 Prius turned to the right on its own. After an mg2 replacement. The direction did not say to disconnect the steering column inside. I noticed a lot of force being pulled on the steering column inside. The boot wad pulled way down. I also replaced the front struts, and after an alignment the car still turned to the right easier than to the left. I took it to the dealer they said the rack nut recall had already been done. I hooked up my scanner and tried to perform the torque initialization. At first it said it couldn't do it. But then, it tried and failed. I noticed there was another screen on the step that said only errors C1515 or C1581 could be present to do the next step. I cleared all the errors then noticed the C1516 initialization needed kept coming back.
     
    #10 Q*bertZ, Oct 24, 2022
  11. Q*bertZ

    Q*bertZ Member

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    Where is the EMPS ECU? Behind the glove box?
    20221024_095911.jpg
     
    #11 Q*bertZ, Oct 24, 2022
  12. ChapmanF

    ChapmanF Senior Member

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    What are the codes now?

    It might be worth checking the electrical outputs of your torque sensor (see the troubleshooting instructions for C1511–C1514). It is a pair of physical potentiometers down inside the steering rack in Gen 1, and known to get wonky with age. (Later Prius generations changed it to use magnets and non-contact sensors.)

    It's possible if the signal coming back from the sensor isn't reasonable, the ECU is saying "nope, I will not believe that is the zero point". The C1516 troubleshooting instructions say to replace the rack if you have tried the calibration three times with no better success.

    Yes, the ECU is behind the glove box, but I would be thinking an ECU issue is probably less likely than the known torque sensor deterioration.
     
    #12 ChapmanF, Oct 24, 2022
  13. Q*bertZ

    Q*bertZ Member

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    I still only get error C1515 and C1516.

    I don't have that book.
     
    #13 Q*bertZ, Oct 24, 2022
  14. ChapmanF

    ChapmanF Senior Member

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    #14 ChapmanF, Oct 24, 2022
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