Cruise control... any ideas?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Questolicious, Feb 11, 2022.

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  1. Questolicious

    Questolicious Junior Member

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    Hi all, I have a 2005 Prius. Cruise control is not working. I've tried the usual diagnostics suggested in this thread, but no luck.

    - All buttons on steering wheel work in all positions (so doesn't indicate broken clock spring)
    - All 3 brake lights work (so doesn't indicate broken brake light switch)
    - Cruise control has never worked for me at all, I'm the third owner, previous owner said he didn't use it so I don't know how long it's been this way
    - No history of accidents that I know of
    - Replaced cruise control stem, no change
    - Replaced ABS pump/brake booster/brake accumulator, no change

    What else can I try here, besides trying to replace clock spring and/or brake light switch and hope it helps?
     
    #1 Questolicious, Feb 11, 2022
  2. JC91006

    JC91006 Senior Member

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    Why did you replace the ABS pump? That has nothing to do with the cruise control and it's a very expensive repair

    Maybe there are stored codes
     
    #2 JC91006, Feb 11, 2022
  3. ChapmanF

    ChapmanF Senior Member

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    Watch the cruise control switch and brake inputs in Techstream live data while working the switches, see if the inputs are arriving as they should.
     
    #3 ChapmanF, Feb 11, 2022
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  4. Questolicious

    Questolicious Junior Member

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    The ABS pump was failing anyway, that was a separate repair which I included here for completeness
     
    #4 Questolicious, Feb 11, 2022
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    I don't know which thread you are referring to for diagnosing the cruise control system, but it sounds like alot of work to replace parts without much actual testing.

    Me, I'm lazy. I would rather sit around and read a few pages of the service manual so I can understand how it works. Then use a scantool to check all systems on the car for codes, and maybe "ask" it why it won't operate the cruise control. You can look in data to see if the proper ecu's are receiving signals from the control switch.

    IF there is something wrong with the control circuits, THEN you can follow the diagnostic procedures (and the wiring diagrams) to determine if the fault could be the clockspring, or other wiring in the car.

    It's certainly possible that only one segment in the clock spring has gone bad- and that's affecting the C/C, but I don't like throwing parts at a problem.

    Test, don't guess. OK, maybe guess ONE time- then do testing if/when that doesn't fix it.

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Feb 11, 2022
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  6. Questolicious

    Questolicious Junior Member

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    Will the miniVCI setup show these inputs? I don't own Techstream or any miniVCI at the moment. My understanding is that I'd need to buy a separate laptop running 32-bit Windows 7 as well, so ballpark $100 to get set up with miniVCI.
     
    #6 Questolicious, Feb 11, 2022
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    Cruise control is not working.
    Replaced ABS pump/brake booster/brake accumulator, no change

    Holy mackerel....Was that job done due to other symptoms or just due to CC not working?
     
    #7 TMR-JWAP, Feb 11, 2022
  8. Questolicious

    Questolicious Junior Member

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    @TMR-JWAP haha no, that job (which was admittedly looooong) was done due to other symptoms.

    I did disassemble the dash tonight just enough to lay eyes on the brake light switch and verify that it does have 4 pins (i.e. is cruise control-enabled).
     
    #8 Questolicious, Feb 12, 2022
  9. TMR-JWAP

    TMR-JWAP Senior Member

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    Looks like I asked the question in post7 before your moderated post 4 showed up. Glad to hear there were other symptoms that made it a requirement.

    Yes, $100 is a good ballpark number. The usual techstream package includes a small cd rom and the cable for connecting to the car. There are many available now that will also work on 64 bit computers. I've had both. The 64 bit is much faster and has better sample rates. A lot of people perfer to have a stand-alone computer just to use the techstream. There's no telling what else may be included with that 'techstream' cd, lol. Prior to using on your car, disconnect from all wireless on the laptop, otherwise the program will try to contact its "update" system and it will lock up.
     
    #9 TMR-JWAP, Feb 12, 2022
  10. Questolicious

    Questolicious Junior Member

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    Got set up with Techstream (wow, what a pain, but it's finally working).

    Inside the program:

    - unfortunately no codes in the Cruise Control module
    - confirmed brake light switch is working correctly (goes from OFF to ON)
    - vehicle speed registers correctly (goes from 0 MPH to current MPH)
    - but when I press the CC on/off button on the stem, nothing happens (was OFF, stays OFF)

    I think that conclusively rules out the brake light switch. Can't rule out that both the original and the new stems are bad, but it's a low-failure part, so seems pretty unlikely. Clock spring is still a possibility.

    Any other ideas, other than taking it to a mechanic?
     
    #10 Questolicious, Feb 15, 2022
  11. TMR-JWAP

    TMR-JWAP Senior Member

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    Clockspring makes sense to me.....

    They're a dime a dozen at a salvage yard
     
    #11 TMR-JWAP, Feb 15, 2022
  12. Questolicious

    Questolicious Junior Member

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    I have working cruise control!

    New clock spring did the trick. Old cruise control stem works fine.

    Confirming that the ONLY symptom of the failed clock spring was lack of cruise control. All the other buttons on the steering wheel were working fine.
     
    #12 Questolicious, Feb 28, 2022
  13. ChapmanF

    ChapmanF Senior Member

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    Yep ... there are a handful of independent circuits that go through the spiral cable. So they all get the same amount of wear over the years from spinning the wheel back and forth, but that doesn't mean they have to fail together, or that there'll be much rhyme or reason to which one happens to go first.

    That was a good process for finding the issue. See in Techstream that pressing the cruise ON/OFF button doesn't show up in the live data.

    That already tells you it's either the CC switch, the spiral cable, or the wire harness from the spiral cable to the ECU.

    If you hadn't wanted to just try the spiral cable and see what happened, the easy next steps would have been to unplug the switch from the spiral cable and test the switch with a multimeter, which would tell you if the switch was the issue. If it wasn't, unplugging the spiral cable from the wire harness and testing there would have revealed which of those two was at fault.
     
    #13 ChapmanF, Feb 28, 2022
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  14. mr_guy_mann

    mr_guy_mann Senior Member

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    #14 mr_guy_mann, Mar 1, 2022
  15. Jonnydwolf

    Jonnydwolf Junior Member

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    Such a good group of people on here, very helpful.
     
    #15 Jonnydwolf, Mar 5, 2022
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