After Replacing Electric Power Steering – Now Having Issues

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Sharter0N, Mar 24, 2025.

  1. Sharter0N

    Sharter0N Junior Member

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    Hello I just replaced the electric power steering unit in my Prius (Gen 2) because the old one had a known failure (sticking/juddering, plus knocking sounds). The replacement unit is confirmed to be 100% functional, but after installation, I’m experiencing a weird issue:

    • At a standstill, the steering is light and smooth (normal).

    • Once moving, the steering becomes noticeably heavier and doesn’t return to center—if I turn left and release the wheel, it stays turned instead of self-centering.
    Questions:

    1. Does a new unit require coding/recalibration in a Gen 2 Prius?

    2. Could this be a sensor issue (e.g., torque sensor or steering angle sensor)?

    3. Any known fixes for the heavy steering/lack of return-to-center?
    Notes:

    • The old EPS had classic failure symptoms (knocking, sticking), but this new issue only appeared after the swap.

    • No warning lights on the dash.
    Thanks in advance for any advice!
     
  2. Tombukt2

    Tombukt2 Senior Member

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    What your car is this and what is the name of the power unit on the sticker there are two different models two different power units they will interchange plug into the box on the dash with the same plugs and all that but they're different names I was just curious which one you were using and what your car you have I'm getting ready to do this myself on an '07 car with an '05 part and I have an '09 part both parts are pretty much the same and they both have different manufacturer names on them The '07 car is experiencing the sticking off center I think to the left literally driving down the road when you come off center it'll make a clunk like it's something coming unstuck a gear something. So when you replace this and took it out you got the yolk to line up properly and all that stuff everything is tight I guess so so center is really center? I can't imagine the steering angle sensor or the linear valve offset causing you that kind of problem just switching out the steering support mechanism unless the steering angle sensor has lost its calibration which you would need either an AP200 scanner or TS software to look into that I guess that's remotely possible I would figure it would just use the steering angle value or the whatever value it had already stored in the computer I don't think it's stored in them I think that's got something to do with the what is it the clock spring.
     
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    The service info mentions using a capable scantool to perform torque sensor zero point initialization then zero point adjustment.

    I might want to look at data from the EPS ecu - there's torque sensor values (& current zero point values for the sensors). Desired and actual current values for the steering boost motor, etc.

    Posted via the PriusChat mobile app.
     
  4. Tombukt2

    Tombukt2 Senior Member

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    I see in T S there are sr I e procedures for steering . Just run thru those . I just pulled the T S computer out to look . Not sure if AP can do it.
     
  5. ChapmanF

    ChapmanF Senior Member

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    Back in the day when I had steering gear torque sensor issues in a gen 1 and I didn't have any scan tool that could read the values, I datalogged them the old-school way.

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