My car idle speed actuator connector has 3 pins. Disconnected the plug from the actuator, and key at on position, and each pins are individually grounded with multimeter, the multimeter reads 12.60 v for the 2 pin, about 1.56 volts each for 1 and 3 pins. Surprise, why pins 2 and 3 are giving voltage reading. Shouldn't they give 0 volts???

  • We would need to know the make/model/year/engine of your vehicle to provide a good answer.
    – SteveRacer
    Jun 27, 2019 at 2:35
  • Hyundai i20 1.2 2011 petrol India version
    – Thang Tons
    Jun 27, 2019 at 15:05

1 Answer 1


I got this from a 1.6 liter Hyundai manual (we don't have the 1.2 in the USA) but the operation is exactly the same.

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The voltage you are seeing is probably the result of a "pull-up" resistor on the grounding transistors inside the ECU.

  • Is this pull up resistor normal??
    – Thang Tons
    Jun 28, 2019 at 14:48
  • @ThangTons Yes, completely normal. It biases the transistor so that it does not have a path to ground unless energized. As a result, it creates a "phantom" voltage on those two signal lines when not active.
    – SteveRacer
    Jul 1, 2019 at 22:51
  • But why the rpm still at 650 from normal 850 after having cleaned the TB unit, ISCV??? Also, I try resetting the computer memory by disconnecting the battery and reconnect after 15 minutes. Still then, no change. Still 650!!! Please kindly advise. Thanks.
    – Thang Tons
    Jul 2, 2019 at 2:44
  • I would check and clean the ISCV and make sure the Throttle Position Sensor (TPS) is adjusted correctly.
    – SteveRacer
    Jul 2, 2019 at 2:52
  • Yes, have done all cleaning including iscv, TB unit etc etc... still 650 rpm
    – Thang Tons
    Jul 2, 2019 at 3:02

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