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Check enging / Idle sensor??

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by junglemom, Jul 19, 2010.

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  1. junglemom

    junglemom New Member

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    I am new to this so please bear with me.. The check engine light came on in my 05 so took my local shop and they checked the code and said it was the Idle Sensor?? They were not able to make the repair. Since then the light went off for a few days then came back on. I now notice the gas motor does not turn off when I stop at a traffic light. Any help?
  2. Bob64

    Bob64 Sapphire of the Blue Sky

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    What code was it?
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  3. junglemom

    junglemom New Member

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    not sure about the code they may have told me, but all I remember is that it was the idle sensor.
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Perhaps you mean the throttle position sensor. Since your gasoline engine does not turn off when the car is stopped, that is proof that something is wrong.

    Without the DTC we can't really comment other than to encourage you to take your car to your local Toyota dealer for repair. Good luck.
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  5. Mike Dimmick

    Mike Dimmick Active Member

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    There is no idle sensor in the Prius. Idling is commanded by the HV ECU when the engine is very cold (coolant temperature below 40°C), when it first warms up to full running temperature (idle check, takes 10 seconds to complete when you come to a stop) and when the HV battery is low and needs recharging. Otherwise it stops the engine when you come to a stop.

    Idling is controlled by the electronically-controlled throttle - the HV ECU asks the Engine ECU to idle, and the Engine ECU adjusts the throttle to change the idle speed appropriately. It checks that the throttle blade moved to the right position using a position sensor. (This actually has two separate channels which are cross-checked.)

    There is a DTC relating to idle control, P0505 Idle Control System Malfunction. It indicates that the measured idle speed is either notably higher or lower than the speed it was trying to achieve (presumably it varies the throttle amount to try to gain control before reporting the DTC), or that the amount of air required to keep the engine idling is either very high or very low.

    The service manual says to check that the PCV (Positive Crank-case Ventilation) hose is correctly connected and is undamaged, and that there are no leaks in the air intake. If those are both OK, it says to check that the throttle body is good - that it closes properly, that the reported position is the actual position, that there is no clogging, and that the blade moves smoothly without rattling.

    If the PCV hose is relevant I'd also check that the PCV valve is working properly. Some owners have reported that it sticks and that this causes problems. If this hasn't been replaced it might be worth doing. It's a $5 part and screws into the end of the engine cover.
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  6. junglemom

    junglemom New Member

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    Thanks for all the information. I took it to the dealer they attempted to clean but were unsuccessfull. They determined that it was a "P0505 Idle Control System Malfunction" they quoted me $1300. to replace.
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    How many miles on the odometer?
    Exactly what is being replaced: the throttle body and motor, or ??
  8. junglemom

    junglemom New Member

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    I have 112,000 miles on the vehicle and the estimate if I can read the writting correctly says throttle with motor body assembly.
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    MSRP on that part is $875.
    Champion ToyotaWorld

    So, $425 for labor, the throttle body gasket, etc. Pretty high, but what can you do.
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  10. vertex

    vertex Active Member

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    According to the manual:
    P0505 Idle Control System
    Malfunction
    - Open or short in idle
    speed control (ISC)
    valve circuit
    - Idle speed control
    (ISC) valve has stuck
    closed
    - ECM
    - Air induction system​
    - PCV valve and hose

    The testing sequence is:

    1 ​
    CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0505)

    Display (DTC output) Proceed to
    P0505 A
    P0505 and other DTCs B​
    GO TO RELEVANT DTC CHART​
    1NZ-FXE ENGINE CONTROL SYSTEM ​
    – SFI SYSTEM ES–291

    ES​
    A
    OK:
    PCV hose is connected correctly and has no damage.
    NG
    OK​
    (a) Check for vacuum leaks in the air induction system.​
    OK:
    No leakage in the air induction system.
    NG
    OK​
    2 ​
    CHECK CONNECTION OF PCV HOSE
    REPAIR OR REPLACE PCV HOSE

    3 ​
    CHECK AIR INDUCTION SYSTEM
    REPAIR OR REPLACE AIR INDUCTION
    SYSTEM

    CHECK ELECTRIC THROTTLE CONTROL SYSTEM

    Make sure they tested everything on this list before changing the TB. Acutally, I doubt that the TB needs replacement, maybe just TPS, which is about $60 if I remember correctly.
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  11. PA Prius

    PA Prius Member

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  12. PA Prius

    PA Prius Member

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    I'm continuing to have the P0505 code on occasion. When I asked our local Toyota dealer about it possibly being the PCV, he said the Prius doesn't have any....

    Regarding my previous post and wondering whether the gas smell in the garage had anything to do with this. The answer is "No," that was the rusted through gas tank on our Chevy S10.

    PA P
  13. ZitterZap

    ZitterZap New Member

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    What happens if this is not changed?
    Does the engine die?

    Just curious
  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    In the case presented by the OP, the problem was that the engine refused to die (or turn off) when it was supposed to. If she didn't have the repair work done, it is likely that the engine would continue to behave that way.
  15. suk

    suk New Member

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