Check Engine Light, Engine Knock

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Marcilla Smith, Jan 9, 2019.

  1. Marcilla Smith

    Marcilla Smith Active Member

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    When accelerating, I am hearing a rattling sound that to me sounds like engine knock. This started only a few weeks ago on my 2005 with 278K miles.

    More recently, the CEL came on. When I went to AutoZone, they pulled the following codes:

    P0125 - Insufficient Coolant Temperature for Closed Loop Fuel Control

    C1231 - Steering Angle Sensor Circuit Malfunction

    U0073 - Control Module Communication Bus A Off
    U0123 - Lost Communication With Yaw Rate Sensor (YRS) Module
    U0124 - Lost Communication With Lateral Acceleration Sensor (LAS) Module
    U0126 - Lost Communication With Steering Angle Sensor (SAS) Module
    U0293 - Lost Communication With Hybrid Powertrain Control Module

    To be clear, this was after resetting the light, and then waiting for it to come back on after <50 miles.

    As for the communication and related codes, I told the gentleman at AZ that the VSC light had been on due to a DOME fuse which continues to blow. He agreed that was a likely cause of those codes.

    As for the P0125, his suggestion was to replace the thermostat and ECT
     
  2. SFO

    SFO Senior Member

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    You may have other DTCs stored, best to find another compatible scanner and see if you can pull anything else.

    Have you checked *all* of the engine fluids lately? (also be sure to check inside the radiator, and not just the coolant overflow tank)

    Did you notice any turbulence on the liquid surface in the inverter reservoir after removing the lid/cap?

    With that mileage you should also check and clean the MAF sensor.

    Here is the workup for DTC P0125 :

    https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8CPDF%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip0125a.pdf

    Here is the workup for DTC C1231 :

    https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8CPDF%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/21avn/cic12313.pdf
     
  3. JC91006

    JC91006 Senior Member

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    VSC = vehicle stability control? Not sure a dome light is the cause
     
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  4. Skibob

    Skibob Senior Member

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    Last time my 4 runner had an engine knock it was old spark plugs. When was the last time your spark plugs were changed?
     
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  5. padroo

    padroo Senior Member

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    I don't think a lot of people know where the actual radiator cap is because it is hidden. All they see if the coolant overflow reservoir.
     
  6. Marcilla Smith

    Marcilla Smith Active Member

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    TY for the replies!

    The radiator, overflow, and inverter coolant reservoirs are all full. The inverter coolant is turbulent with the car in "ready."

    (Yes, I went to the actual radiator cap underneath the black plastic piece that goes between the headlights :: wink :: )

    Following the workups, the first one says I need to go to pg 05-55, and the second says I need to first resolve the U0126 issue.

    As for the VSC, I can't explain why the DOME (light) fuse being out affects it, I only know that's what I've read (and that it basically serves as a fuse for several different devices that require power when the vehicle is not necessarily running).

    Regarding spark plugs, I have not changed them since purchasing the vehicle in March of last year, so it's anyone's guess when they were last replaced
     
    #6 Marcilla Smith, Jan 9, 2019
    Last edited: Jan 9, 2019
  7. edthefox5

    edthefox5 Senior Member

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    Hows the engine oil level after it has sat for a while?

    How many times have you run the engine so low on oil it threw a check engine light or a Red Triangle of Death?
     
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  8. Marcilla Smith

    Marcilla Smith Active Member

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    After sitting for a couple of hours, the oil level was a little under the lower mark. That's where I usually keep it, based on recommendations I've read to run it a little under. Do you suggest otherwise?

    As for the car's history of notifications given for oil levels too low, I can't say as I only purchased the vehicle less than a year ago, already with >260K. What are you saying?

    I'd like to follow the workups, although to progress further, I'd need access to pg 05-55 and to the U0126 guide, if SFO or someone else could please provide more information
     
  9. Raytheeagle

    Raytheeagle Senior Member

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    I believe the recommendations are to keep it just below the high mark;).

    Keeping it just below the low mark is: too low and damage to the engine being starved of oil will result.

    I would change my oil management routine to avoid further damage(y).
     
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  10. edthefox5

    edthefox5 Senior Member

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    Don't run it lower than the full mark. The full mark is there for a reason. There's not alot of oil in this engine to begin with it requires every drop.
    The run it lower nonsense came from this site years ago when posters thought they were getting better mileage running the oil lower.

    Check it every weekend first thing before starting the car. You have a high mileage car it probably eats alot of oil.
     
  11. Skibob

    Skibob Senior Member

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    Run it below the lower mark? The owners manual says to ADD oil when it reaches that mark. What kind of moron would say to run oil below the add mark in ANY car?
     
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  12. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If in fact you (and/or prior owners) allowed the engine oil level to remain below the lower dimple on the dipstick, then you should expect that inadequate lubrication resulted in abnormal engine wear.

    Excessive clearance in a bearing is causing the engine knock sound. The remedy is to replace the engine. 278K miles logged on the odometer reflects excellent service received from the car, time to get another.
     
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  13. Mendel Leisk

    Mendel Leisk Senior Member

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    I would suspect a short time below the low mark on the dipstick would be ok, but yeah, not good.
     
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  14. edthefox5

    edthefox5 Senior Member

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    When I joined this site in 2007 everybody said that. SMH. Some idiot thought he was getting great great mileage running the oil lower and everybody jumped on it because everybody was crazed for mileage then. Maybe they still do but I could give a sh*t I'm just trying to keep the car on the road at this point. Best way to do that is keep the oil at the full line. Keep the inverter fluid at the full line. Keep the trans fluid at the full line.

    Its not rocket science.
     
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  15. Marcilla Smith

    Marcilla Smith Active Member

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    Thank you, Ed, for restoring my faith in my sanity. I don't recall having ever seen that fuel economy was the reason. If I had, like you, that would not be enough to convince me to take the risk!

    Consequently, I've now added oil to a point over halfway to the top dimple. I intend to add some more later.

    In the meantime, something quite embarrassing has come to light... To put the bottom line up front, the "rattling noise" may have actually been a rattle and not a "knock." I started noticing there was at least one other distinct rattling, then I noticed the rattle(s) started to occur even with no accelerator. This led me to believe it was a loose body piece which was imitating an "engine knock."

    At some point on my trip back from Florida, the piece either rattled itself back into place or fell off. All of the rattles (whether any were actually engine-related or not) are gone now, and I can no longer duplicate them, even when trying to do so.

    Still, the CEL remains :: sigh ::
     
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  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    You should replace the engine thermostat as mentioned in your OP.
     
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  17. Skibob

    Skibob Senior Member

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    I don’t think anyone questioned your sanity, there is a lot of bad or mis information on the internet. You don’t know how qualified someone is when you get an answer. One time when I was changing the head gasket on my 95 Civic a Honda site poster said to save money and use the 96 3 layer metal head gasket rather than the updated 95 5 layer metal gasket. When I checked the gasket 1 or 2 coolant holes were covered. He and several other posters had no idea what they were talking about. Always be Leary of free information on the internet.
     
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  18. Marcilla Smith

    Marcilla Smith Active Member

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    In what I pray is the final update :: crosses fingers :: the CEL went off on its own and has stayed off for several days now :: tentatively wipes sweat from brow ::
     
  19. Marcilla Smith

    Marcilla Smith Active Member

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    CEL came back. Thermostat was replaced. Will see if CEL goes away. Next step will be to replace the sensor
     
  20. Marcilla Smith

    Marcilla Smith Active Member

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    CEL/MIL returned after thermostat was replaced almost 3 weeks ago. Before I change the sensor, I came across this thread listing a TSB about recalibrating the ECM. I tried posting to that thread, but when I check the forum, it does not show as bumped :: scratches head ::

    In any event, is this something I can do myself with an aftermarket Techstream, or will I need to take this to a hybrid specialist mechanic?
     
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