P1120
HyundaiHyundai Specific: Throttle Position Sensor (TPS) Circuit Range/Performance Problem
Medium SeverityThis code indicates that the vehicle's engine control unit, or ECU, has detected an issue with the electrical signal from the Throttle Position Sensor. This means the ECU isn't accurately seeing how much the throttle is open, which can lead to problems with engine performance and fuel delivery.
⚠️ Before You Begin (Safety First)
Before performing any work, always ensure the vehicle is parked on a level surface with the parking brake engaged. To prevent accidental electrical shorts or injury, disconnect the negative battery terminal before working on electrical components. Be cautious when the engine is running, as parts can be hot and moving.
Common Symptoms
- Reduced engine power or sluggish acceleration
- Rough idle or stalling
- Hesitation during acceleration
- Check Engine Light illuminated
- Cruise control may not work
Common Causes
- Faulty Throttle Position Sensor (TPS) itself, where the internal resistance is no longer correct
- Corroded or loose electrical connections at the TPS
- Damaged wiring in the TPS circuit, such as a short or open circuit
- Problem with the throttle body assembly causing the TPS to bind or not move freely
- Less commonly, an issue with the Engine Control Unit (ECU) processing the TPS signal
Frequently reported on: Hyundai Elantra (2001-2006), Hyundai Sonata (1999-2005), Hyundai Santa Fe (2001-2006), Hyundai Tiburon (2003-2008), Hyundai Accent (2000-2005)
Diagnostic Steps
- The first step is always to visually inspect the Throttle Position Sensor and its wiring harness. Look for any obvious signs of damage, corrosion, or loose connections. This can often reveal simple issues.
- Next, with the ignition off and the battery disconnected, gently unplug the TPS connector. Inspect the pins inside the connector for bending, corrosion, or dirt. Clean them if necessary using electrical contact cleaner.
- Using a multimeter, you'll need to test the TPS sensor's resistance and voltage readings. Typically, with the ignition on (engine off), you'll measure the reference voltage (usually 5V), ground, and signal voltage while slowly opening and closing the throttle. The signal voltage should sweep smoothly from low to high without any drops or spikes. This tells us if the sensor is sending a clean signal.
- If the TPS readings are erratic or outside specifications, the Throttle Position Sensor likely needs to be replaced. Ensure you get the correct part for your Hyundai model. Sometimes the TPS is integrated into the throttle body and the entire assembly must be replaced.
- After replacement, clear the P1120 code using an OBD-II scanner and test drive the vehicle. Pay close attention to engine performance and acceleration to confirm the repair was successful. Always recheck for codes afterwards.
👨🔧 When to Call a Professional
If you've checked the basic connections and cannot pinpoint the issue after going through the diagnostic steps, or if the symptoms are severe enough to make the car undrivable, it's time to consult a professional technician who has specialized diagnostic equipment.
Commonly Asked Questions
What exactly does the Throttle Position Sensor do?
The Throttle Position Sensor, or TPS, is essentially a potentiometer, like a dimmer switch, that tells the vehicle's computer exactly how far open the throttle plate is. When you press the accelerator pedal, the throttle plate opens, and the TPS sends a corresponding voltage signal to the Engine Control Unit. This signal is crucial for the ECU to calculate the correct fuel injection and ignition timing.
Can I drive with a P1120 code?
While you might be able to drive the vehicle, it's generally not recommended for extended periods. The P1120 code indicates the ECU isn't getting reliable throttle position data, which can lead to unpredictable engine behavior like stalling, poor acceleration, or a rough idle. This can make the car unsafe to drive and potentially lead to other engine damage over time. It's best to address it promptly.
Is it possible for a dirty throttle body to cause a P1120 code?
Yes, absolutely. If the throttle body is excessively dirty, carbon buildup can prevent the throttle plate from moving smoothly or closing completely. This physical impediment can cause the Throttle Position Sensor to report an 'out of range' signal, even if the sensor itself is good. Cleaning the throttle body is often a good first step, especially if you notice hesitation or rough idle.
Do I need to recalibrate the new Throttle Position Sensor after replacement?
For many modern Hyundai vehicles, the ECU will automatically 'learn' the new TPS sensor's range over a few drive cycles. However, some models or specific throttle body designs might benefit from a manual 'throttle body relearn' procedure using a professional scan tool, especially if the new sensor causes idle issues. Always check your vehicle's service manual for specific procedures.
What's the difference between 'out of range' and 'performance problem' for the TPS?
Good question! 'Out of range' typically means the sensor's signal is consistently too high or too low, beyond the expected minimum or maximum values. A 'performance problem' usually indicates that the signal might be within the correct overall range but is intermittent, jumpy, or doesn't change smoothly as the throttle is opened and closed. Both mean the ECU isn't getting reliable information from the sensor.