Comprehensive Diagnostic Guide: OBD-II Code P0120 - Throttle Position Sensor A Circuit Malfunction
Quick Answer
What P0120 Means
Comprehensive : OBD-II Code P0120 - Throttle Position Sensor A Circuit Malfunction. This affects your vehicle's fuel and air metering system.
Most Likely Cause
Multiple possible causes - see diagnostic details below
Many causes can be addressed by experienced DIYers.
Generally safe to drive short-term. Have it diagnosed soon.
Safe to Drive (Short-Term)
Generally safe to drive short-term. Have it diagnosed soon.
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Detailed Diagnostic Information
What This Code Means
- Open Source definition: P0120 is described as a malfunction of the Throttle Position Sensor A circuit (TPS A). In other words, the PCM is detecting an out-of-range or erratic signal from the primary TPS circuit. Source wording in the provided Open Source listing:
- Context in OBD-II framework: OBD-II codes are organized as Powertrain Codes (P-codes). P0120 is categorized as a Powertrain Code, indicating a drivetrain/engine management sensor circuit issue rather than an emissions-only fault. This classification is noted in the OBD-II reference material (Powertrain Codes section).
Symptom overview: what real-world drivers often notice with P0120
Note: The following items are common owner-reported symptoms associated with TPS A circuit issues. They reflect typical complaints seen with P0120 in practice (not guaranteed to appear on every vehicle).
- Check Engine Light (MIL) may come on.
- Hesitation or sluggish acceleration when pressing the accelerator.
- Intermittent or variable throttle response, including occasional lag or surges.
- Erratic idle behavior or idle fluctuations (particularly if the TPS reading is not matching pedal position).
- In some cases, little to no noticeable driveability impact if the PCM detects a fault but the vehicle continues to run.
This diagnostic guide was generated using verified reference data:
- Wikipedia Technical Articles: OBD-II
- Open-Source OBD2 Data: N/A (MIT)
Content synthesized from these sources to provide accurate, real-world diagnostic guidance.
Consider professional help if:
- You are not comfortable performing the diagnosis yourself
- The issue requires specialized tools or equipment
- Initial repairs did not resolve the code
- Multiple codes are present simultaneously
- The vehicle is still under warranty
Frequently Asked Questions
What does code P0120 mean?
P0120 indicates Comprehensive Diagnostic Guide: OBD-II Code P0120 - Throttle Position Sensor A Circuit Malfunction. This is a powertrain code related to the fuel and air metering system. When your vehicle's computer detects this condition, it stores this code and may illuminate the check engine light.
Can I drive with code P0120?
You may be able to drive short distances with P0120, but it should be addressed soon. Extended driving could lead to additional problems or increased repair costs.
How much does it cost to fix P0120?
Repair costs for P0120 typically range from $100-$800, depending on the root cause and your vehicle. Diagnostic fees are usually $50-$150, and actual repairs vary based on whether parts need replacement. Get multiple quotes for the best price.
What causes code P0120?
Common causes of P0120 include sensor malfunctions, wiring issues, mechanical failures in the fuel and air metering system, or related component wear. The specific cause requires proper diagnosis with a scan tool and visual inspection.
Will P0120 clear itself?
P0120 may temporarily clear if the underlying condition improves, but the root cause should still be diagnosed. If the problem persists, the code will return.
Related Diagnostic Codes
Important Disclaimer
This information is for educational purposes only. We are not licensed mechanics. Always consult a certified mechanic for diagnosis and repair. Improper repairs can be dangerous.
Helpful Resources
Last updated: 2025-11-26