P0120
UniversalThrottle/Pedal Position Sensor/Switch A Circuit Malfunction
High SeverityThis code indicates an issue with the electrical circuit for the Throttle Position Sensor (TPS) or Accelerator Pedal Position Sensor (APP sensor) A. A malfunction in this circuit can lead to incorrect throttle input readings, significantly affecting engine performance and drivability.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before working on electrical components. Be extremely cautious if experiencing uncontrolled acceleration or deceleration, and pull over safely immediately.
Common Symptoms
- Check Engine Light illuminated
- Reduced engine power or "limp home" mode
- Erratic or no throttle response
- Engine surging or stalling
- Difficulty accelerating
- Cruise control not working
Common Causes
- Faulty Throttle Position Sensor (TPS) or Accelerator Pedal Position Sensor (APP sensor).
- Corroded, loose, or damaged wiring/connectors in the sensor circuit.
- Short circuit or open circuit in the sensor wiring.
- Problem with the Engine Control Module (ECM/PCM) (less common).
- Faulty throttle body (if TPS is integrated).
Frequently reported on: General Motors (various models 1999-2007), Ford (various models 2000-2009), Toyota (various models 2000-2008)
Diagnostic Steps
- Inspect the Throttle Position Sensor (TPS) or Accelerator Pedal Position Sensor (APP sensor) and its wiring for visible damage, corrosion, or loose connections.
- Check the electrical connector for bent pins or corrosion.
- Using a multimeter, test the voltage and resistance of the sensor according to service manual specifications.
- If testing confirms a faulty sensor, replace it with a new one, ensuring proper calibration if required.
- Clear the fault code and test drive the vehicle to verify the repair.
👨🔧 When to Call a Professional
If the vehicle exhibits erratic acceleration, stalling, or enters a "limp home" mode, it is crucial to have it professionally diagnosed immediately to ensure safe operation.
Commonly Asked Questions
Can I drive with a P0120 code?
It is not recommended to drive with a P0120 code as it can lead to unpredictable throttle response, reduced power, or sudden stalling, which is unsafe.
Is the Throttle Position Sensor (TPS) the same as the Accelerator Pedal Position Sensor (APP)?
While both measure throttle input, the TPS is on the throttle body, and the APP sensor is on the pedal. P0120 can refer to either, depending on the vehicle's design and which A circuit is implicated.
How much does it cost to fix a P0120?
The cost can vary from $100-$300 for a new sensor and DIY labor, up to $300-$600 or more if professional diagnosis and replacement are needed, or if the throttle body needs replacement.
Can a dirty throttle body cause P0120?
A very dirty throttle body can sometimes affect the TPS readings or cause it to stick, but P0120 typically points to an electrical circuit malfunction rather than just a dirty throttle body.
Do I need to calibrate a new TPS/APP sensor?
Some vehicles may require a relearn procedure or calibration using a scan tool after replacing the TPS or APP sensor. Consult your vehicle's service manual.