P0121 Code: Throttle Position Sensor/Switch Circuit Range/Performance
🟠 Moderate severity · drivable
Drivable, but the throttle reading is off, which can cause hesitation and poor idle.
What P0121 means
The throttle position sensor (TPS) is reporting a reading that doesn't match expected engine conditions. The TPS tells the computer how far the throttle is open so it can deliver the right amount of fuel.
Symptoms
- Check engine light is on
- Hesitation or surging under acceleration
- Rough or unstable idle
- Poor fuel economy
Common causes
- most common: Faulty throttle position sensor
- common: Worn or dirty throttle body
- less common: Wiring or connector problem at the TPS
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Clean the throttle body | Yes | $10–40 |
| Replace the throttle position sensor | Yes | $50–150 |
| Repair TPS wiring or connector | Mechanic | $50–150 |
Frequently asked questions
Can I drive with a P0121 code?
Yes, but you may notice hesitation and rough idle. Fix it soon for smooth running.
What is the most common cause of P0121?
A faulty throttle position sensor. Cleaning the throttle body is a good first step before replacing it.
How much does it cost to fix a P0121?
Typically $50–$150 for a new throttle position sensor.
Related codes
P0122
P0122 Code: Throttle Position Sensor/Switch Circuit Low Input
P0123P0123 Code: Throttle Position Sensor/Switch Circuit High Input
P0120P0120 Code: Throttle Position Sensor Circuit
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.