P0121 — Throttle Position Sensor/Switch A Circuit Range/Performance
Category: Powertrain Severity: Medium
Updated:
DTC code P0121 means: Throttle Position Sensor/Switch A Circuit Range/Performance. It falls under the "Powertrain" category, with an estimated severity of Medium. Common causes include worn TPS track, dirty throttle body and poor connector contact; it's worth confirming the diagnosis before replacing parts.
Possible causes
- Worn TPS track
- Dirty throttle body
- Poor connector contact
- Disagreement with the MAF reading
Symptoms
- Bucking at steady speed
- Harsh shifts (automatic)
- Rough idle
- Check engine light
How to diagnose it step by step
- Clean the throttle body.
- Sweep the TPS signal from 0 to 100%.
- Check the connector.
- Replace the sensor if there are dropouts.
How to fix it
Clean the throttle body and watch the TPS signal while slowly pressing the pedal: any dropout means a worn sensor.
Estimated repair cost
$40–120 (sensor) or $200–600 (throttle body).
Frequently asked questions
What does DTC code P0121 mean?
Throttle Position Sensor/Switch A Circuit Range/Performance.
Is code P0121 serious?
Severity Medium. Not urgent, but worth diagnosing to avoid bigger damage.
Can I keep driving with code P0121?
Drive with caution.
Related codes
P0120 P0122 P0123 P0125 P0128 P0118 P0117 P0116 P0115 P0113
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