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Cruise Control Issue (Can it be activated with OBD2 or TechStream?)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by carbon, Sep 21, 2021.

  1. carbon

    carbon The Knight Templar

    Apr 9, 2013
    2005 Prius
    Hello PriusChat, nice to see everyone again! I recently have been having problems with my Cruise Control arm on my 2005 Prius Gen 2, need some info from those more knowledgeable here to diagnose the problem.

    Quick summary:
    1. CC activation light ("CRUISE" on HUD) was intermittent for a while, sometimes it would activate when pressed, other times nothing.
    2. CC activation light eventually stopped working. CC did not work even without the light.
    3. I ended up replacing the CC arm on the steering wheel with an OEM part. Still nothing.

    Now I need to diagnose exactly what the problem is.
    I've read all the posts on here, nothing conclusive.

    Some say its the Clock Spring.

    • Buttons on my wheel work at all positions, except the "info" button under map on right side.
    • Rotated the wheel in all directions and tried to activate CC, didn't activate.

    Some say its the brake light actuator.

    • I tried engaging CC at all different positions rotating the wheel, while holding the brake pedal "up" ( as in, foot under the pedal, pulling towards me) nothing engaged, read about this tip from another thread here on PriusChat.

    Normally the CC light can be engaged even when under 25MPH but not activated until going above that.

    The car is not in B mode.
    My foot is not resting on the brake pedal.
    All 3 Brake lights activate when I hit the brake.
    The car does indicate "Ready".

    My question: is there a way I can connect OBD2 / TechStream and flip a bit or two to see if CC is activated? Or can I activate the CC system via TechStream?

    If I am able to do this, then I can rule out a few possibilities, such as the LED being burned out on the dashboard. I can see if the system is receiving the On-Off/ RES / CANCEL / etc signals.

    My current best guess is that this is the clock spring in my wheel, as ONE button doesn't work on the right side of my wheel (info button doesnt, the rest work). Note: I have the old nav + voice package and some buttons don't work while that screen is up anyway.
  2. JC91006

    JC91006 Senior Member

    Nov 10, 2013
    Los Angeles, CA
    2008 Prius
    If your car has been in an accident where the clock spring may have been replaced before, there's a good chance the clock spring is not an original part and is having the issues you're experiencing.
    carbon likes this.
  3. ChapmanF

    ChapmanF Senior Member

    Mar 30, 2008
    Indiana, USA
    2010 Prius
    I think this is a good guess.

    For test purposes, you could backprobe a wire into the cruise on/off pin of the connector on the stationary side of the clock spring, and ground* that, and see if your cruise reliably turns on or off each time you do.

    * where I say "ground" here, be careful. I think if you look at the wiring diagram, the different functions of the cruise switch share a single wire, by connecting it through different resistances to ground. So if you backprobed a wire in there. you'd need to test by grounding it through a resistor of the same value as the on/off button of the switch.

    I think the wiring diagram shows where the resistances are, but not what their exact values are. Best bet might be to find out with an ohmmeter on the old cruise switch if you still have it (or just use the old cruise switch in the test).
    carbon likes this.
  4. mr_guy_mann

    mr_guy_mann Senior Member

    Sep 3, 2020
    2006 Prius
    If you have (or can get) Techstream, then you can go into data for the hybrid control ecu and see if it reports the cruise control switch signals as changing state correctly. The diagram shows the switch as having 2 wires- a (around) 12V signal wire and a ground. As ChapmanF pointed out, pressing each button briefly connects that signal wire to ground- either directly ("On/Off") or through resistors for the others.
    So pressing a button should pull the signal voltage down to a different value for each one. You could backprobe and measure that voltage at the cruise switch, at the column end of the clock spring, or at the connector for the hybrid ecu ("behind" the glove box next to ECM)- it should be the same value at all 3 points.

    here is some info from my 06 manual
    CC1.jpg CC2.jpg CC3.jpg
    Posted via the PriusChat mobile app.
    #4 mr_guy_mann, Sep 22, 2021
    Last edited: Sep 22, 2021
    carbon likes this.