P0120
Throttle/Pedal Position Sensor A Circuit Malfunction
The engine computer is not trusting the main throttle or accelerator pedal position signal. The sensor circuit may be open, shorted, or sending an unstable reading. This can cause hesitation, reduced power, poor throttle response, or limp mode.
- SEV
- 3/5
- DRIVE
- CAUTION
- DIY
- $20-$200
- SHOP
- $120-$550
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Faulty throttle position sensor A or accelerator pedal position sensor A
- Damaged, loose, or corroded wiring or connector in the sensor A circuit
- Open circuit, short to ground, or short to voltage in the sensor A signal or reference wiring
Typical repair cost
DIY usually runs $20-$200. Typical shop repair lands around $120-$550, depending on the root cause.
01 / Definition
P0120 sets when the PCM detects a malfunction in throttle position sensor or accelerator pedal position sensor A circuit. Unlike range or correlation codes, this fault points more broadly to a circuit problem such as an open, short, unstable signal, poor terminal contact, or an internally failed sensor. Depending on platform design, the fault may come from the throttle body, the pedal assembly, shared 5-volt reference wiring, or the PCM's signal monitoring.
02 / Drive status
With caution. The vehicle may still move, but throttle response can be delayed or limited without much warning. Avoid heavy traffic and high-speed driving until the circuit fault is diagnosed.
03 / Symptoms
- Check engine light
- Poor throttle response
- Hesitation on acceleration
- Reduced engine power
- Limp mode
- High or unstable idle
- Stalling in some cases
04 / Causes
| 1 | Faulty throttle position sensor A or accelerator pedal position sensor A | high |
|---|---|---|
| 2 | Damaged, loose, or corroded wiring or connector in the sensor A circuit | high |
| 3 | Open circuit, short to ground, or short to voltage in the sensor A signal or reference wiring | high |
| 4 | Throttle body or pedal assembly internal fault affecting the A signal | medium |
| 5 | Poor 5-volt reference or sensor ground shared with other engine sensors | medium |
| 6 | PCM fault or software issue after circuit and component tests pass | low |
05 / Diagnostic sequence
- 01Confirm P0120 and check for related throttle, pedal, and correlation codes.
- 02Inspect the throttle body, accelerator pedal connector, and wiring harness for loose pins, corrosion, rub-through, or water intrusion.
- 03Use live data to watch throttle or pedal sensor A voltage while slowly moving the pedal or throttle through its range.
- 04Look for a stuck value, sudden dropouts, or readings that jump instead of changing smoothly.
- 05Verify 5-volt reference, ground, and signal continuity with a multimeter before replacing parts.
- 06Wiggle the harness and connectors during testing to catch intermittent opens or shorts.
- 07If wiring checks out, test the throttle body or pedal assembly according to the platform service information.
- 08Clear codes, perform any throttle relearn required by the vehicle, and retest after repairs.
06 / Repairs
| 1 | Repair damaged wiring, corroded terminals, or loose connectors in the throttle or pedal sensor A circuit | $20-$150 |
|---|---|---|
| 2 | Replace the faulty throttle position sensor, pedal sensor, or integrated pedal assembly if testing confirms an internal failure | $60-$350 |
| 3 | Replace or service the throttle body if the sensor A fault originates inside the throttle assembly | $150-$450 |
| 4 | Restore 5-volt reference or ground circuit faults and perform throttle relearn if required | $50-$200 |
| 5 | Update or diagnose the PCM only after the sensor and wiring circuits pass testing | $100-$550 |
07 / Related codes
08 / FAQ
Does P0120 mean the throttle body is bad?
Not always. The throttle body can be at fault, but wiring, connectors, the pedal assembly, or the shared reference circuit are also common causes.
Can a bad accelerator pedal cause P0120?
Yes. On many drive-by-wire vehicles the pedal assembly contains one of the monitored position sensors and can set P0120 when it fails.
Can I drive with P0120?
Sometimes, but it is risky to ignore because throttle response may become limited or erratic. It should be diagnosed before normal driving continues.
What is the difference between P0120 and P0121?
P0120 is a broader circuit malfunction code, while P0121 usually means the signal is present but out of expected range or performance.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.