What is the solution? P0121 The TPS has been replaced.?

The P0121 codes from Auto Zone read as follows:


BBTPS/Pedal Position sensor / Switch "A" circuit BBrange / Perfomance

Probable Cause:

BB1: Poor Electrical Connection (How to fix this? Proper Tune Up?)

BB2: Open Or Short Circuit Condition (How to fix this? Proper Tune Up? Oil Change?)

BB3. Faulty TPS (It was replaced 3 days ago. Was it replaced wrong?)

BB4: Faulty Pedal position Sensor (How do I order this brake switch to replace it? What is it called? A brake switch?)


Its a 98 Hyundai Elantra 1.8L 4 cyl. There is no part called a 'Pedal Sensor' for the year Hyundai. There is a break switch? Is that what needs to be replaced?

5 Answers

  • 1 decade ago
    Favorite Answer

    Ok, I think I help shed some light on this for you. P0121 is for the throttle position sensor. They also said it was for a pedal position sensor but that only applies to cars that come with ETC (Electronic Throttle Control). ETC is also referred to as drive by wire. Newer cars use an electric motor to open and close the throttle plate in the throttle body as opposed to earlier or non-ETC cars that use a cable that connects the gas pedal to the throttle. ETC uses a throttle position sensor built into the ETC throttle body assembly and a pedal position sensor to tell the computer how far to open the throttle. In your case, I don't think you have ETC but you need to look at the throttle body and see if there is a cable connected to it that goes to the gas pedal or if there is an electrical connector on the throttle body that has more than 3 wires. If you have a non-ETC engine, you still have a problem with the TPS sensor. Since you say you already replaced the TPS sensor, that tells me you have a non-ETC engine. The TPS should have 3 wires going to it. One is the signal wire that goes to the computer. The other two wires are the 5v supply and the 5v return, or sensor ground. You need to check to see what the sensor reading is at the computer and if you have good 5v to the sensor. You would do most of this testing with a digital volt ohm meter. You would also need to check the wires for continuity and for proper resistance in the wires. It sounds like you may have a trip to a qualified service repair center in your future.

    Source(s): Former ASE master certified gm dealer service/diagnostics technician, Engineering technician for Delphi Powertrain Systems, I have been installing and testing ETC systems for several years, mostly on Hyundai cars.
  • 1 decade ago

    Hmmm. bbking48 is right. Now, having the TPS sensor replaced is a good step forward. The question is: was the TPS installed properly? If you don't fit it properly in place, the check engine light would not disappear.

    Your Elantra is definitely not equipped with ETC. The fact that Auto Zone is telling you is the "pedal position sensor" at fault, this doesn't make sense. The only so called "pedal position sensor: might be the brake switch!!! Who knows?...

    Why don't you go to Hyundai dealer to have a proper diagnostic done? At leas they can give you the right information and tell you exactly what the fault code is?

    Its your choise.

    Good luck.

    Source(s): Hyundai dealer-service Manager
  • Anonymous
    7 years ago

    I did replace the TPS on my 2002 Elantra and I still get occasional weird shifting driving at constant speeds. You mentioned that it has to be installed properly. Is there some way to check that? The check engine light is currently off, but will sometimes come on for a day or so and then go off again. What would you suggest?

  • reinke
    Lv 4
    4 years ago

    P0121 Throttle Position Sensor

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  • Anonymous
    5 years ago

    p0121 tp circuit range performance problem. the code means that the computer is having a problem limiting the voltage going to the sensor to begin with. most sensors aside form the o2 use a 5 volt Reference voltage the sensor drops that voltage to what it needs to be to represent the signal that is needed. te sensor was not the problem.

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