P0120
UniversalThrottle Pedal Position Sensor/Switch A Circuit Malfunction
The engine control system has detected a problem in the electrical circuit for throttle pedal position sensor or switch A. This input tells the system how far the driver is pressing the accelerator. A faulty signal can affect engine response or cause the vehicle to limit acceleration. The code does not by itself prove that the sensor needs replacement.
⚠️ Before You Begin (Safety First)
If the accelerator response becomes unpredictable, the engine loses power, or the vehicle cannot maintain a safe speed, pull over somewhere safe and arrange assistance. If the vehicle responds normally, drive cautiously and have the fault checked promptly.
Common Symptoms
- The check-engine warning light may be on because the control system detected a circuit fault.
- Acceleration may be weak, delayed or inconsistent if the system receives an unreliable pedal-position signal.
- The vehicle may limit engine response as a protective measure.
- The engine may idle or drive roughly if the fault affects how the system interprets accelerator input.
- There may be no noticeable symptoms, particularly if the fault is intermittent.
Common Causes
- A fault within the throttle pedal position sensor or switch A.
- A loose, damaged or corroded connector or wiring in the sensor circuit.
- A problem with circuit power, ground or signal continuity.
- An intermittent electrical connection that changes with vibration or pedal movement.
- A control-module or related circuit fault, considered after the sensor and wiring have been checked.
Diagnostic Steps
- Note whether the accelerator response has changed, and avoid driving if it is unpredictable or unsafe.
- With the vehicle safely parked, visually check accessible wiring and connectors associated with the throttle pedal position circuit for obvious damage, looseness or corrosion. Do not force connectors or probe terminals.
- Check for other stored diagnostic codes with a compatible scan tool and record them before clearing anything; related codes can help direct diagnosis.
- If a scan tool can display pedal-position data, observe whether the reading changes smoothly as the pedal is moved, following the vehicle-specific instructions. An abnormal reading needs circuit diagnosis and does not alone identify the failed part.
- If the code returns or the checks do not identify the issue, have the circuit tested using the correct wiring information for the vehicle.
When to Call a Professional
Use a scan tool to review related codes and observe the pedal-position signal while the pedal is moved. Inspect the circuit and connectors, then test wiring, power and ground against vehicle-specific service information. Confirm the fault before replacing a sensor or considering a control module issue.
Compare component listings
Confirm diagnosis and vehicle fitment before buying. A listing does not prove that a part needs replacement. We may earn a commission from qualifying purchases.
Commonly Asked Questions
Does P0120 prove the throttle pedal position sensor is defective?
No. The code identifies a detected circuit malfunction. The sensor, its connector, wiring, power or ground, and related control circuitry may need to be checked before deciding what to repair.
Can I keep driving with P0120?
It depends on how the vehicle responds. If acceleration is limited, inconsistent or unpredictable, stop driving when it is safe and arrange assistance. If it behaves normally, drive cautiously and seek diagnosis promptly.
What does the A circuit label mean?
It identifies the circuit designation used in this fault description. The exact circuit layout and test procedure depend on the vehicle's model, year and engine.
Could a wiring problem cause this code?
Yes. A damaged wire, poor connection, or power or ground problem can disrupt the sensor circuit and produce a malfunction even when the sensor itself is not the cause.
Browse Available Code Guides
Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.