1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Knock sensor bad?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Aaron Vitolins, Mar 5, 2016.

  1. Aaron Vitolins

    Aaron Vitolins Senior Member

    Joined:
    Feb 28, 2014
    1,612
    1,144
    0
    Location:
    Franklin TN
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Hey guys! I'm back, here on PC after a long time. I've been busy with work and moving. It's good to be back!

    My good ole trusty Prius is still running good, change the oil every month (3000-5000 miles) and still drinks oil and a little over half a qt ever 1000 miles.. No big deal. Well over the last 20,000 miles I started to notice this off rattle, noise when accelerating mid throttle mostly when up hill. I thought it may have been the timing chain after changing the water pump, spark plugs and using all sorts of fuel additives, but no change.

    After time it's only gotten worse, my works buys my fuel (regular 87) but one day I brought my self a tank of super premium, and hey!!! It sounded great, quiet, powerful, I loved driving again!

    My question is.. Is this because of a worn timing chain making the knock sensor do this, is this because of carbon in the engine? What should I know? What do you think. I really need to fix this. My work buys me regular fuel and I would like to keep it that way! Thank you so much guys! Sorry about the long post, had to give some background☺
     
    #1 Aaron Vitolins, Mar 5, 2016
  2. 69shovlhed

    69shovlhed Surly tree hugger

    Joined:
    May 13, 2012
    2,170
    746
    0
    Location:
    Delaware
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Premium
    could be carbon build up. you'd need a borescope to look into the combustion chambers to verify. if the knock sensor was bad it should set a code.
     
    #2 69shovlhed, Mar 5, 2016
  3. Aaron Vitolins

    Aaron Vitolins Senior Member

    Joined:
    Feb 28, 2014
    1,612
    1,144
    0
    Location:
    Franklin TN
    Vehicle:
    Other Hybrid
    Model:
    N/A
    True! Another question, is there any in between (working like new, and not working at all) for Knock sensors? I know all the Toyota products I've had experience with won't throw a code till the part is completely failed or the problem is very bad. Thanks for your reply!
     
    #3 Aaron Vitolins, Mar 5, 2016
  4. valde3

    valde3 Senior Member

    Joined:
    Jun 28, 2014
    2,002
    745
    0
    Location:
    Finland
    Vehicle:
    2004 Prius
    From Toyota manual:
    “A flat type knock sensor (non–resonant type) has the structure that can detect vibration in a wider band of the frequency from about 6 kHz to 15 kHz...”
    “P0325 Knock sensor signal level remains at low for more than 10 seconds
    P0327 Output voltage of the knock sensor is 0.5 V or less
    P0328 Output voltage of the knock sensor is 4.5 V or more”
    “TYPICAL ENABLING CONDITIONS
    The monitor will run whenever the following DTCs are not present
    Battery voltage 10.5 V or more
    Idle OFF
    Time after engine start 5 seconds or more
    Engine coolant temperature 60C (140F) or more
    Intake air amount per revolution 0.3 g/rev or more”

    So as long as engine warms up to more than 60c/140F (which it will unless you have faulty thermostat) and you have no other faults codes that would affect you do get code for non-working knock sensor.
     
    #4 valde3, Mar 5, 2016
  5. 69shovlhed

    69shovlhed Surly tree hugger

    Joined:
    May 13, 2012
    2,170
    746
    0
    Location:
    Delaware
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Premium
    I suppose it is possible for the sensor to be failing and not quite bad enough to throw a code. if the sensor isn't too expensive or difficult to get to, it might be worth trying a new one. but if there is excessive carbon build up, that would be treating the symptom, not the cause.
     
    #5 69shovlhed, Mar 5, 2016
  6. Aaron Vitolins

    Aaron Vitolins Senior Member

    Joined:
    Feb 28, 2014
    1,612
    1,144
    0
    Location:
    Franklin TN
    Vehicle:
    Other Hybrid
    Model:
    N/A
    So let's just say it in fact carbon, what would I do to clean my engine of this?
     
    #6 Aaron Vitolins, Mar 5, 2016
  7. Aaron Vitolins

    Aaron Vitolins Senior Member

    Joined:
    Feb 28, 2014
    1,612
    1,144
    0
    Location:
    Franklin TN
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Thinking I should try and replace the knock sensor, it doesn't seem to expensive. Is this a difficult job? Does anyone know where it's located?
     
    #7 Aaron Vitolins, Mar 9, 2016
  8. andrewclaus

    andrewclaus Active Member

    Joined:
    Sep 15, 2009
    993
    324
    0
    Location:
    Golden, CO
    Vehicle:
    2007 Prius
    I haven't done the job on the Prius, but from the Toyota parts diagram it looks like it's near the top of the engine block, right in the front center behind the the intake manifold and throttle body and that means some work. Once it's exposed, it's just a 10 or 12 mm nut and a harness connector.
     
    #8 andrewclaus, Mar 9, 2016
  9. Aaron Vitolins

    Aaron Vitolins Senior Member

    Joined:
    Feb 28, 2014
    1,612
    1,144
    0
    Location:
    Franklin TN
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Great! I'll check it out once I get back from utah, I've taken off the air cleaner box assembly before so I can take it off again and see if I can get a good look where it is. Appreciate your reply
     
    #9 Aaron Vitolins, Mar 10, 2016
  10. PriVusLY

    PriVusLY Junior Member

    Joined:
    Sep 21, 2005
    30
    0
    0
    Location:
    Appleton, WI
    I have the symptoms where the knocking/pinging occurs only under moderate load/acceleration.
    Does not occur under light or heavy acceleration.
    Anybody fix those symptoms with a knock sensor replacement?
    This forum thread: Easy Knock Sensor Replacement | PriusChat
    covers an "easy" method to replace the knock sensor. Anybody out there think that will work for a 2006?
     
    #10 PriVusLY, Apr 11, 2017
(You must log in or sign up to post here.)