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
- Throttle Body
- Throttle Position Sensor
- Wiring Harness
Most often, it is dirty and simply needs to be cleaned but can also have damaged components.
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, be used to clean the unit.
Example Throttle Body and Air-Intake Cleaner on Amazon
CRC 05078 Throttle Body and Air-Intake Cleaner – 12 Wt Oz.
The onboard computer (ECM) receives data from the position sensor.
When the sensor goes bad, the ECM will think there is an issue since that is receiving information.
Replacing the throttle position sensor is a DIY task done by many backyard mechanics but if in doubt, be sure to take your vehicle to a professional.
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.