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Thread: OBD2 throttle position PID

  1. #1
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    Nov 2010
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    Lightbulb OBD2 throttle position PID

    Hi All,

    I was experiencing some problem while reading throttle position. I was reading PID 0x11 as I don't know which one to read. But as I accelerate, the pedal position(0x11) value is not smoothly read. It suddenly increases to 86% even if I have applied throttle around 30%.

    What is the difference between PID no. 0x11,0x45,0x47,0x48,0x49,0x4A,0x4B.

    0x11 - Throttle position
    0x45 - Relative throttle position
    0x47 - Absolute throttle position B
    0x48 - Absolute throttle position C
    0x49 - Accelerator pedal position D
    0x4A - Accelerator pedal position E
    0x4B - Accelerator pedal position F

    Which is the best to read the throttle position? I believe 0x11 but then whats the significance of rest of them?

    Thanking you in advance.
    Nirav

  2. #2
    VENDOR - ScanTool Vitaliy's Avatar
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    Nirav,

    "Throttle position" and "pedal position" are different things. On some cars, there is no direct coupling between the two: the pedal simply controls a potentiometer and the throttle is controlled by the ECU.

    A single throttle plate can have up to three throttle position sensors (A, B, and C).

    "Absolute throttle position" means the TP is reported as "seen" by the ECU. On most cars, the lower value will be above 0%, and upper value will be below 100%.

    "Relative throttle position" means the "learned" TP position. The ECU calculates the voltage offset for the closed-throttle position, and uses it as the 0%. If the offset voltage is higher than 0V, then you never get to 100% even for WOT.

    Clear as mud?

    Vitaliy
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  3. #3
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    Join Date
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    Quote Originally Posted by Vitaliy View Post
    Nirav,

    "Throttle position" and "pedal position" are different things. On some cars, there is no direct coupling between the two: the pedal simply controls a potentiometer and the throttle is controlled by the ECU.

    A single throttle plate can have up to three throttle position sensors (A, B, and C).

    "Absolute throttle position" means the TP is reported as "seen" by the ECU. On most cars, the lower value will be above 0%, and upper value will be below 100%.

    "Relative throttle position" means the "learned" TP position. The ECU calculates the voltage offset for the closed-throttle position, and uses it as the 0%. If the offset voltage is higher than 0V, then you never get to 100% even for WOT.

    Clear as mud?

    Vitaliy
    Hi Vitaliy,

    Thanks for the explaination. It was really helpful.

    Nirav

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