Unable to complete Linear Valve Offset after actuator replacement

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by farmermac, Apr 21, 2026 at 8:35 AM.

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  1. farmermac

    farmermac Junior Member

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    Working on a 2008 Prius with 165k miles. The actuator in the car had a bad accumulator that would leak down and the pump would run every 15 seconds. I got a used actuator that was sold as tested from someone with excellent history of selling these. I've installed it, bled the car using a techstream twice, but i've found myself unable to complete the linear valve procedure. There is only a single code in the entire car, for C1345 not learning linear valve offet (and accompanying C1368 linear valve offset).

    I've followed the factory steps by clearing the memory first, and the procedure goes through the motions - you can head the various valves and pistons making noise as the brakes are actuated. I don't believe there's air in the system. the pedal feels firm and will lock the tires up on a test drive.

    The steering angle sensor is reading a bogus value (-1050 degrees or something similar) and doesnt respond to steering input. I have a suspicion that this is causing the linear valve offset calibration not to finish, as the ecu isnt capable of determining a baseline value for the steering angle, but trying to get someone's attention that may be knowledgeable to help me confirm before I throw parts at it.
     
    #1 farmermac, Apr 21, 2026 at 8:35 AM
  2. ChapmanF

    ChapmanF Senior Member

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    The steering angle reading may be a red herring, because of the way the car self-calibrates it. The reading is always something bogus when you've just turned the car on. As soon as you've driven a small distance straight ahead (which can be recognized from the yaw sensor reading zero and the wheel speeds being equal), the ECU decides "ok, that's what zero steering angle is" and the readings make sense after that.

    Sometimes a used actuator might just not be able to have an offset within specification. I mean, I'd probably give it several more tries with the bleeding and learning in the hope of not spending more money, but if it still doesn't work that could be the answer.
     
    #2 ChapmanF, Apr 21, 2026 at 9:38 AM
  3. farmermac

    farmermac Junior Member

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    Quick question though - the steering angle sensor should register a value when turning the steering wheel - and it doesnt in this case. It stays at -1050 at all times, regardless of steering wheel position. My confusion stems from the car not throwing a code for implausible angle sensor or bad reading. But, it appears that you work on toyotas for a living, and didnt know if the gen2 logic of the skid ecu throws a code for this condition or not, in your experience. No matter what, angle sensor isnt ever changing both on my techstream and Autel scanner.

    I am assuming for this calibration procedure to complete successfully, that a functional angle sensor is required at the very least before i write off the actuator as bad?
     
    #3 farmermac, Apr 21, 2026 at 10:07 AM
  4. ChapmanF

    ChapmanF Senior Member

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    I don't have a gen 2 handy at the moment to go out and check. I remember being baffled the first time I did look at the angle reading from a gen 2 right after power on, and couldn't make any sense of it until I had studied how the self-calibration works. It was long enough ago that I don't remember whether the initial bogus reading was a bogus reading that changed when I turned the wheel, or just a bogus reading that remained until the car was in motion and the readings became real.

    You could maybe look at that on somebody else's Prius before deciding it means your sensor is bad.

    I'm not sure that the steering angle sensor would prevent solenoid offset learning in any case. I see that the offset-learning instructions (gen 3 anyway, no gen 2 manual in front of me ATM) do say to make sure the steering is centered ... but I'm not sure that means the car is depending on that sensor reading in the learning process.
     
    #4 ChapmanF, Apr 21, 2026 at 10:21 AM
  5. farmermac

    farmermac Junior Member

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    the gen 2 manual i have access to also says that the steering wheel must be centered as a condition. I will check wiring between angle sensor and wherever it goes to before replacing real quick, i guess. I appreciate the time you took to answer. I have a gen 3 on hand that does respond (as every normal car does when you turn the wheel with a working sensor)...I've found your answers while googling to be well informed and its probably about as good as im going to get. This seems obvious, but the car's been a basket case prior to getting to me from all kinds of hacks, but generally the computers are excellent at throwing errors when appropriate (for example, due to out of range or implausible reading) so i figured id ask someone that may have more specific knowledge

    ill try going for a 22mph+ drive to see if the computer starts displaying sensor data. How finicky are those linear valves if the pump is good and the accumulator holds pressure? this this the second time i do this job on this car and i was really hoping this actuator would be good. Its a car i own (customer car would only get new). Initial actuator as it came couldnt hold pressure, second one - used - had a bad pump and couldn't build pressure, this one seems to be acting normal in all ways besides the linear valve unable to calibrate.
     
    #5 farmermac, Apr 21, 2026 at 10:26 AM
    Last edited: Apr 21, 2026 at 10:31 AM
  6. JC91006

    JC91006 Senior Member

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    Make sure your 12v battery is fully charged. If you still can't perform the function, then the actuator is bad.

    Used parts are just not reliable. if a person has a "history" of selling these, he's just a used part sales guy that gets them from junk yards. any of those can be borderline failed units
     
    #6 JC91006, Apr 21, 2026 at 11:27 AM
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  7. ChapmanF

    ChapmanF Senior Member

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    The actuator got simplified in some ways from gen 2 to gen 3. Gen 3 just has two linear solenoids, while its eight wheel-specific apply and release solenoids just open and close. Gen 2 had linear apply and release valves for each wheel. So I imagine gen 2's linear-solenoid calibration process is more involved and a used gen 2 actuator has more ways of being a little off.
     
    #7 ChapmanF, Apr 21, 2026 at 11:39 AM
  8. farmermac

    farmermac Junior Member

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    Any idea about the steering angle sensor in particular in this case
     
    #8 farmermac, Apr 21, 2026 at 11:45 AM
  9. JC91006

    JC91006 Senior Member

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    You only have a code for the car. Before chasing these gremlins, do you have a good 12v battery? Without a good charged battery, it cannot complete the linear valve offset. This is done with the engine off, not in Ready mode. The errors you're getting can be related to a weak 12v, reporting bogus errors.
     
    #9 JC91006, Apr 21, 2026 at 12:01 PM
  10. farmermac

    farmermac Junior Member

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    Yes, I do. I'm using a heavy duty battery maintainer/charger at my shop that is able to keep a solid 13v+ throughout the procedure. Im not real familiar with this type of braking system but work on cars all day every day. Do you know if the linear valve calibration requires a functional angle sensor reading? The procedure requires a reset of the yaw + angle sensor values before starting.
     
    #10 farmermac, Apr 21, 2026 at 12:13 PM
  11. JC91006

    JC91006 Senior Member

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    if your car didn't have any errors related to the angle sensor before you changed the actuator, then you shouldn't have one now. I've done about 5 of these and the times that I haven't been able to complete the linear valve offset is always a bad actuator or a low 12v battery. A used part is always a pain to work with and when I need to find one, I always find one with the new updated part number (I think it end with 51). Even that updated part number has been out for 10 years so just imagine the old non updated parts, how old they are!
     
    #11 JC91006, Apr 21, 2026 at 12:22 PM
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  12. farmermac

    farmermac Junior Member

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    I hear you...I believe those are all replacement units, too, in that the part number was changed after the car's production run were done. I couldnt find one when i was shopping for these units (44500-47141).
     
    #12 farmermac, Apr 21, 2026 at 12:40 PM
  13. JC91006

    JC91006 Senior Member

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    If I had replied yesterday, you could have gotten a new part for under $1000 from Toyota dealers that were offering additional 25% off parts, off their already low online prices. $967 I believe. But the part number you provided is from Toyota and it includes a resistor as a kit, that's why their part number cannot be found used.

    The actuator part number that's printed on the part is 44510-47050 for the OLD part, and the new updated part is 44510-47051
     
    #13 JC91006, Apr 21, 2026 at 12:49 PM
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  14. farmermac

    farmermac Junior Member

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    Thanks for the info. will change search parameters to this new part number. Just curious if you have any insight into that angle sensor. This car is new to me. purchased as a non runner with lots of deferred maintenance and issues, and there wasnt a code stored initially for the angle sensor, but it is definitely not showing any data in the live data
     
    #14 farmermac, Apr 21, 2026 at 1:02 PM
  15. JC91006

    JC91006 Senior Member

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    I don't have any info to share regarding that angle sensor. I have to say that's not a problem I've encounter in the 2nd Gen, and I've worked on a ton of them 20+
     
    #15 JC91006, Apr 21, 2026 at 1:04 PM
  16. ChapmanF

    ChapmanF Senior Member

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    Shopping for Toyota parts also means contending with the fact that a part will often have a five-digit-dash-five-digit number physically marked on it that is not its part number. Or even more than one such number. Naturally, it can be easy to mistake one of those for the part's actual part number.

    Sometimes, of course, you will find reseller listings online that will have listed the part under one of those numbers, because the reseller placing the listing made the same mistake.

    More about that in ➡this thread⬅.
     
    #16 ChapmanF, Apr 21, 2026 at 1:53 PM
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