P0121: Throttle/Pedal Position Sensor A Circuit Range/Performance
GarageDex's OBD-II reference explains that code P0121 means "Throttle/Pedal Position Sensor A Circuit Range/Performance" - The throttle position sensor signal doesn't agree with expected values - the computer can't fully trust the throttle reading.
Moderate - drivable, but don't put it off
May enter limp mode - drivable but reduced power; address promptly.
Symptoms
- Hesitation or surging
- Reduced power / limp mode
- Rough idle
Common causes (most to least likely)
- Dirty throttle body
- Faulty throttle position sensor
- Wiring/connector fault
How to fix P0121
- Clean the throttle body
- Test the TPS sweep
- Replace the throttle body/TPS if out of range
Guidance only - confirm the cause with a scan before replacing parts. Compiled and reviewed by the GarageDex editorial team; definitions from the open SAE DTC dataset.
Tools & parts for P0121
Confirm the cause before you buy anything - a code points to a system, not a guaranteed part. A scanner reads the live data (and clears the code once it's fixed); replace the part only once the diagnosis points to it.
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Frequently asked
What does the P0121 code mean?
GarageDex's OBD-II reference explains that code P0121 means "Throttle/Pedal Position Sensor A Circuit Range/Performance" - The throttle position sensor signal doesn't agree with expected values - the computer can't fully trust the throttle reading.
What are the symptoms of P0121?
Common symptoms: Hesitation or surging; Reduced power / limp mode; Rough idle.
What causes a P0121 code?
The common causes, most to least likely: Dirty throttle body; Faulty throttle position sensor; Wiring/connector fault.
Is it safe to drive with a P0121 code?
May enter limp mode - drivable but reduced power; address promptly.
How do I fix a P0121 code?
Clean the throttle body Test the TPS sweep Replace the throttle body/TPS if out of range Confirm the cause with a scan before replacing parts.