Diagnostic trouble code P1120 is a manufacturer-specific powertrain code. Because it is manufacturer-specific, its exact definition depends entirely on the vehicle make, model, and application.
Exact vehicle application must be verified before diagnosis. The code identifies a detected condition in a specific throttle or pedal position sensor circuit, but further testing is required.
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Key Takeaways
- P1120 is a manufacturer-specific code, meaning its definition varies between automakers like Toyota, Ford, and General Motors.
- On certain applications, it indicates an accelerator pedal position sensor circuit malfunction or a throttle position sensor out-of-range condition.
- Possible causes include damaged wiring, corroded connectors, carbon buildup, or a failed sensor assembly.
- Symptoms vary by application but can include an illuminated Check Engine Light, poor acceleration, rough idling, or a fail-safe limp mode.
- Diagnosis requires verifying the exact factory definition for the specific vehicle and following the manufacturer’s targeted testing procedures.
P1120 Code Description and Implications
Because P1120 is manufacturer-specific, there is no single universal definition. The exact monitored system and fault condition depend on the vehicle make and model.
When your vehicle’s onboard computer triggers a P1120 fault code, it identifies a detected condition in a specific sensor circuit.
Some Toyota and Lexus applications: P1120 indicates an “Accelerator Pedal Position Sensor Circuit Malfunction,” where the engine control module detects an implausible signal from the pedal assembly.
Certain Ford applications: P1120 designates a “Throttle Position Sensor Out of Range Low” fault, indicating the sensor voltage has dropped below the expected minimum threshold.
Specific General Motors applications: P1120 can indicate a secondary throttle position sensor circuit fault or an out-of-range condition on a specific throttle body circuit.
Common Causes of the P1120 Code
The underlying cause depends entirely on the verified factory definition for the specific vehicle application.
For applications monitoring the accelerator pedal position sensor, possible causes include a failed sensor assembly, damaged wiring in the pedal circuit, or poor electrical grounds.
For applications monitoring the throttle position sensor, causes involve carbon buildup binding the throttle plate, damaged wiring harnesses, corroded connectors, or a failed sensor element.
Symptoms Associated With P1120
Symptoms vary widely depending on the underlying system fault and the vehicle manufacturer.
On applications with an accelerator pedal sensor fault, the primary symptom is an illuminated Check Engine Light accompanied by a fail-safe limp mode, severely limiting engine power.
On applications with a throttle position sensor out-of-range fault, the vehicle may experience rough idling, hesitation during acceleration, stalling, or an inability to maintain a steady cruise speed.
Diagnosing the P1120 Trouble Code
Diagnosis must begin by confirming the exact factory definition for the specific make, model, and year. Attempting to diagnose a throttle body sensor on a vehicle where P1120 indicates an accelerator pedal circuit will lead to misdiagnosis.
For pedal position sensor applications, technicians inspect the pedal assembly wiring for damage and measure the sensor signal circuits for opens, shorts, or erratic voltage drops during pedal movement.
For throttle position sensor applications, diagnosis involves checking the throttle body for carbon binding, verifying the sensor reference voltage and ground, and monitoring the live data for smooth voltage transitions.
Repairing the P1120 Issue
Repairs must follow confirmed diagnosis based on the specific vehicle application.
If testing confirms a failed accelerator pedal position sensor or damaged wiring, the pedal assembly or harness must be replaced, and the system may require a relearn procedure.
If a throttle position sensor or wiring fault is confirmed, the throttle body must be cleaned or the sensor assembly replaced, followed by verifying proper throttle operation.
Cost Considerations for P1120 Repairs
Repair costs depend entirely on the confirmed root cause, component accessibility, and local labor rates.
Cleaning a throttle body or repairing a section of wiring may require minimal parts and labor. Conversely, replacing an integrated electronic throttle body assembly or an accelerator pedal position sensor requires more diagnostic time.
Prevention Strategies for Future Occurrences
Some electrical or mechanical failures cannot be reliably prevented. However, periodically cleaning the throttle body to remove carbon buildup can help prevent mechanical binding that affects throttle position sensor readings.
Inspecting exposed wiring harnesses near the accelerator pedal and throttle body for chafing or moisture intrusion helps reduce the likelihood of circuit faults.
Troubleshooting Tips and Best Practices
Never assume P1120 is a universal throttle position sensor code. Always verify the exact definition for the specific vehicle before purchasing parts or beginning electrical testing.
Do not ignore related codes. A pedal position sensor fault frequently appears alongside other pedal sensor circuit codes, while a throttle position fault may trigger additional electronic throttle control warnings.
Check for technical service bulletins applicable to your exact vehicle application, as manufacturers frequently release updated pedal assemblies or revised throttle body components for recurring circuit faults.
More OBD-II Codes
| P1118 | P1121 | P0121 | P1690 |
| P1119 | P1122 | P0122 | P1662 |
| P1116 | P1123 | P0123 | P1654 |
| P1115 | P1124 | P0220 | P1653 |
| P1114 | P1125 | P1110 | P1111 |
| P1112 | P1126 | P1105 | P1108 |
Frequently Asked Questions
Is P1120 a generic or manufacturer-specific code?
No. P1120 is a manufacturer-specific code. Its exact definition varies significantly between automakers, so the factory service information for the specific vehicle must be consulted.
Can I drive my car with a P1120 code?
It depends on the application. If P1120 indicates a pedal or throttle sensor fault, the vehicle may enter a fail-safe limp mode with severely reduced power, making it unsafe to drive.
Will disconnecting the battery clear the P1120 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying electrical or mechanical fault. The code will return once the module runs its self-test.
Can a dirty throttle body cause a P1120 code?
On applications monitoring the throttle position sensor, heavy carbon buildup can mechanically bind the throttle plate, causing the sensor signal to fall out of the expected range and trigger the fault.
Does P1120 always mean the sensor is bad?
No. While a failed sensor can cause this code, damaged wiring, corroded connectors, poor electrical grounds, or mechanical throttle binding are frequent causes that must be ruled out first.
What Should You Do About the P1120 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application. Because P1120 is manufacturer-specific, identifying whether it relates to the accelerator pedal position sensor or the throttle position sensor is the mandatory first step.
Follow the applicable manufacturer diagnostic steps to test the relevant system and components. Once the root cause is confirmed, complete the necessary repairs and verify that the system operates correctly and the code does not return.
