3 Causes and Fixes P0121 Chevy Silverado

By | January 15, 2023

Causes and Fixes P0121 Chevy Silverado
If you have a Chevy Silverado and get a P0121 error code, there is a problem with the throttle body.

An OBDII scan tool will give the error as “Throttle Position (TP) Sensor 1 Performance.”

Some scan tools will give the error as “Throttle Pedal Position Sensor Switch (TPS) A Circuit Range Performance Problem.”

What is a P0121 OBDII Error Code?

A P0121 error code is “Throttle Position (TP) Sensor 1 Performance.”

The Onboard computer (ECM) is not receiving data on the location of the throttle body.

This information is needed for the ECM to calculate the air and gas ratio mixture; the vehicle will often run badly until it is fixed.

3 Causes and Fixes P0121 Chevy Silverado

  1. Throttle Body
  2. Causes and Fixes P0121 Chevy Silverado Throttle Body
    When a Silverado has a P0121 code, the usual cause is the throttle body.

    Most often, it is dirty and simply needs to be cleaned but can also have damaged components.

    The first thing to do is to clean the debris and gunk out of the throttle body to see if the code will clear.
    Causes and Fixes P0121 Chevy Silverado Throttle Body Dirty
    The inside can get a build-up of black gunk that can cause an issue.

    After cleaning the unit, If the error will not clear or comes back, there is likely another problem.

    Throttle body cleaner can be bought at an auto part store or online that, along with a clean rag, can be used to clean the unit.

  3. Throttle Position Sensor
  4. Causes and Fixes P0121 Chevy Silverado Throttle Position Sensor
    A bad throttle position sensor will also cause a P0121 error code.

    The onboard computer (ECM) receives data from the position sensor.

    When the sensor goes bad, the ECM will think there is an issue since the sensor is sending bad data.

    The position sensor is located on the throttle body and is held in place with clips.
    Causes and Fixes P0121 Chevy Silverado Throttle Position Sensor Location
    It is replaced by removing the harness and clips.

    Replacing the throttle position sensor is a DIY task, but if in doubt, be sure to take your vehicle to a professional.

  5. Wiring Harness
  6. Causes and Fixes P0121 Chevy Silverado Throttle Position Sensor Location
    If the throttle body is cleaned, the sensor replaced, and the error still comes back, there may be an issue with the wiring.

    While rare, a bad pin on the harness or a cut wire can cause problems.

    Examine the harness and the pins going in as well the wires for any bad connection or a cut on a wire.

A Chevy Silverado with a P0121 OBDII error code has a dirty throttle body, bad sensor, or a wiring problem.

The official definition is “P0121: Throttle pedal position sensor A circuit range performance”.

Each component will need to be gone through to see which is the problem.

The first component to check is the throttle body which is usually dirty and needs to be cleaned.

A dirty throttle body is the most common problem, with the error usually clearing after a good cleaning.

If the error does not clear, the throttle position sensor can also cause issues and should be replaced.

If all the above does not work, there may be a wiring problem with a shorted or open wire causing problems.

Have you had problems with a Chevy Silverado and P0121 OBDII error code? Let us know your thoughts below.

Bob Thomas

4 thoughts on “3 Causes and Fixes P0121 Chevy Silverado

  1. Dave Kessinger

    Hi how’s it? I have a 2011 Chevy Silverado and I am having this error code. So I cleaned the throttle body. It was filthy. I replaced the TPS with a AC Delco TPS. Now when I start the truck the idle speed goes up to 3000 and won’t slow down. I disconnected the battery for a couple of minutes and it is still doing the same thing.


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