Check Engine Code
P0121
Throttle Position Sensor / Switch A Circuit Range/Performance
Severity: high
DIY difficulty: 2/5
Typical cost: $50–$500
What P0121 means
The throttle position signal isn't matching what the ECM expects given MAP, engine RPM, and pedal position. On drive-by-wire cars, this can trigger reduced-power mode.
Symptoms
- Check engine light
- Hesitation or surging
- Limp mode (drive-by-wire cars)
- Erratic idle
Likely causes (most common first)
- Failing TPS / dirty resistive track
- Carbon buildup on the throttle plate
- Wiring issue
- Failed throttle body
Can I keep driving?
High — risk of damage if ignored
Typical repair cost
DIY fixes can start near $50 (parts only). Shop repairs for P0121 typically run up to $500 depending on the underlying cause and vehicle. Start with the most common cause — Failing TPS / dirty resistive track — before throwing parts at it.
Related codes
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