P0120 - Throttle/Pedal Position Sensor/Switch A Circuit
P0120 is a generic powertrain diagnostic trouble code indicating Throttle/Pedal Position Sensor/Switch A Circuit. It relates to the Fuel & Air Metering system.
DTC Breakdown (SAE J2012)
| System | Powertrain (P) |
| Type | Generic |
| Subsystem | Fuel & Air Metering |
| Fault Index | 20 |
| Standard | SAE J2012 / ISO 15031-6 |
What does diagnostic code P0120 mean?
The powertrain control module logged P0120 due to a Throttle Position Sensor (TPS) circuit malfunction fault.
Severity Level & Driveability Details
Severity: High
Throttle Position Sensor faults can cause unexpected acceleration or sudden engine stalling, presenting a driveability hazard.
Common Symptoms of P0120
- Engine stumbling, hesitation, or sudden surges.
- Vehicle entering a low-power 'limp home' mode.
- Rough engine idle or engine stalling.
- Check engine light illuminated.
Typical Causes for P0120
- Failed Throttle Position Sensor or throttle body assembly.
- Corroded throttle body wiring connector pins.
- Damaged wiring harness between the sensor and the PCM.
- Loose sensor mounting screws (on older vehicles).
Diagnostic and Troubleshooting Steps
Monitor the Throttle Position percentage on a scan tool to verify it sweeps smoothly from ~10% at idle to ~90% at wide-open throttle without drops or spikes.
Typical Repairs and Fixes
- Replacing the Throttle Position Sensor or the throttle body assembly.
- Cleaning and repairing the wiring harness connector.
- Updating PCM throttle calibration software.
Sensor Location & Parts Involved
The sensor is mounted on the side of the throttle body, connected to the throttle plate shaft.
Clearing Code & Recurrence
Reset the code using a scan tool and perform the throttle body idle relearn.
Emissions & Smog Inspection Impact
Mismatched throttle signals cause incorrect fuel trims, raising exhaust emissions.
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Related Diagnostic Codes
Sources & References
This diagnostic guide is compiled and verified against the following authority sources:
- NHTSA Vehicle Complaints
- SAE J2012 diagnostic guidelines
Frequently Asked Questions about P0120
What does the throttle position sensor A circuit malfunction code P0120 mean?
The powertrain control module logged P0120 due to a Throttle Position Sensor (TPS) circuit malfunction fault.
Is it safe to drive with the throttle position sensor A circuit malfunction code P0120 active?
No, a throttle sensor fault represents a stalling or sudden acceleration risk.
How much does it cost to repair a throttle position sensor A circuit malfunction code P0120 fault?
The sensor itself is $40-$100, while a full electronic throttle body runs $200-$400. Total repair is $150-$600.
What are the common causes of the throttle position sensor A circuit malfunction code P0120?
Trigger conditions for the throttle position sensor A circuit malfunction code P0120 include: Failed Throttle Position Sensor or throttle body assembly., Corroded throttle body wiring connector pins., Damaged wiring harness between the sensor and the PCM..
Can I clear the check engine light for throttle position sensor A circuit malfunction code P0120?
Reset the code using a scan tool and perform the throttle body idle relearn.
Will the throttle position sensor A circuit malfunction code P0120 cause an inspection failure?
Mismatched throttle signals cause incorrect fuel trims, raising exhaust emissions.