Engine shakes after replacing head gasket but no consistent codes

Discussion in 'Gen 3 Prius Technical Discussion' started by oldzebra, Sep 26, 2025.

Tags:
Page 2 of 2
  1. oldzebra

    oldzebra New Member

    Joined:
    Sep 26, 2025
    13
    5
    0
    Location:
    Pacific Northwest
    Vehicle:
    2012 Prius
    Model:
    IV
    Thank you very much, that helps a lot.
     
    #21 oldzebra, Oct 14, 2025 at 5:26 PM
  2. oldzebra

    oldzebra New Member

    Joined:
    Sep 26, 2025
    13
    5
    0
    Location:
    Pacific Northwest
    Vehicle:
    2012 Prius
    Model:
    IV
    I back probed the cam sensor to start. I'm not sure what values I should have gotten. Here are the readings, Do these readings look like what they should look like?

    Voltage:
    White to black wire: +4.1V falling to .71V when a metal object is held to the end of the sensor
    Red to Black: .89V
    Red to White: 5.02V

    Ohms:
    R to White: 1.35K Ohms
    R to Black: 1.29K Ohms

    Thanks
     
    #22 oldzebra, Oct 14, 2025 at 9:25 PM
  3. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
    Jun 6, 2008
    9,938
    6,129
    7
    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    It would help to know the code. However to check for an open you measure each wire for ohms from one end to the other with the ecm disconnected and powered off. Typically you want 1 ohm after accounting for meter lead ohm readings by themselves. You then check each wire to chassis which should be higher than 10k.

    See attached
     

    Attached Files:

    #23 rjparker, Oct 14, 2025 at 10:19 PM
  4. oldzebra

    oldzebra New Member

    Joined:
    Sep 26, 2025
    13
    5
    0
    Location:
    Pacific Northwest
    Vehicle:
    2012 Prius
    Model:
    IV
    I'll hook up techstream today to verify that the code is actually what my reader says it is. Based on this forum, generic readers, like the ones I have, are less than reliable.

    I'm not very good at troubleshooting car electrical issues. Thanks for explaining clearly what I should do. If the code is still there with tech stream I'll go from the ECU to the cam wiring to check for an open.
     
    #24 oldzebra, Oct 15, 2025 at 1:07 PM
  5. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
    Jun 6, 2008
    9,938
    6,129
    7
    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    I suspect you don't have an "open" cam sensor based on your voltage reading changes, even though they were not exactly what the manual suggests.

    These three codes each have one possibility for an open circuit but have other options for mechanical timing issues, which is more common.

    IMG_0323.jpeg

    This video covers the timing chain positioning in detail. A problem that has happened was use of the wrong marks. This link jumps to that section. The whole video shows the rest of the process except rotating the chain counterclockwise to release the tensioner.

    Sane Auto Jump to Cam Timing Marks
     
    #25 rjparker, Oct 15, 2025 at 1:51 PM
    Last edited: Oct 15, 2025 at 1:57 PM
(You must log in or sign up to post here.)
Page 2 of 2