P0120 — Throttle Position Sensor / Switch A Circuit Malfunction
The ECU detects a general electrical fault on the throttle position sensor/switch A circuit. Signal missing, implausible, or wiring broken. Generic catch-all when no more specific TPS-A code applies.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Throttle position sensor
- Tps wiring
- Tps connector
- Throttle body
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- TPS worn or failed (dead spot in resistive track)
- TPS wiring or connector fault
- TPS mechanically misaligned to throttle shaft
Possible symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
- Reduced-power or limp mode may occur
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.