P1120 Code: Here's How to Solve It Fast

The P1120 trouble code is a diagnostic trouble code (DTC) that indicates an issue with the throttle position sensor (TPS) in a vehicle. Specifically, it signifies that the TPS is reporting a position that is out of the expected range, which can lead to various performance issues. This code is often triggered when the Engine Control Module (ECM) detects a discrepancy between the actual throttle position and the desired position as determined by the vehicle's programming. Understanding this code is crucial for vehicle owners and DIY mechanics, as it can affect engine performance and drivability.

P1120 Code Meaning	P1120 Code Common Causes
Throttle Position Sensor Out of Range	Damaged or defective throttle position sensor
Inconsistent throttle position readings	Corroded or shorted wiring/connectors
Limp mode activation	Improper throttle body adjustment
Engine performance issues	Failed or malfunctioning ECM
Illuminated check engine light	Faulty accelerator pedal position sensor (APP)

Symptoms of P1120 Code

When dealing with a P1120 code, several symptoms may arise, indicating that your vehicle requires attention:

• Stored trouble code and illuminated check engine light: The most immediate sign of a P1120 code is the illumination of the check engine light on your dashboard.
• Engine power loss: Drivers may notice a decrease in engine power, which can range from mild to severe, potentially leading to immobilization of the vehicle.
• Rough or erratic idling: The engine may struggle to maintain a stable idle, resulting in fluctuations in RPM.
• Harsh or unpredictable gear shifts: Automatic transmission vehicles may experience erratic shifting patterns due to incorrect throttle position readings.
• Activation of limp mode: The vehicle's ECM may enter limp mode as a safety precaution, limiting power and functionality to prevent further damage.

Technical Explanation of P1120 Code

The P1120 code specifically relates to the throttle position sensor's ability to correctly report the position of the throttle plate within the throttle body. The ECM relies on this information to adjust fuel injection and ignition timing for optimal engine performance. When the actual position deviates from what is expected—typically within a range of 3.42% to 9.85%—the ECM triggers the P1120 code.

Throttle Position Sensor Functionality

The TPS is essentially a potentiometer that varies its resistance based on the throttle plate's position. As you press the accelerator pedal, the TPS sends voltage signals back to the ECM. If these signals fall outside acceptable parameters, it can indicate:

• A malfunctioning TPS
• Wiring issues such as shorts or corrosion
• Problems with related components like the accelerator pedal position sensor

Step-by-Step Diagnosis for P1120 Code

Diagnosing a P1120 code involves several steps:

1. Check for additional codes: Use an OBD-II scanner to check if there are any other related DTCs stored in addition to P1120.
2. Visual inspection: Examine wiring and connectors associated with the TPS for signs of damage, corrosion, or loose connections.
3. Test TPS voltage: Using a multimeter, measure the voltage output from the TPS while manually moving the throttle plate. The voltage should change smoothly without any dropouts.
4. Inspect accelerator pedal position sensor: If applicable, check the APP sensor for proper operation as it can also contribute to throttle control issues.
5. Perform a throttle body reset: If any components have been replaced or adjusted, perform a throttle relearn procedure according to manufacturer specifications.
6. Check ECM functionality: In rare cases, if all other components are functioning properly but issues persist, consider testing or replacing the ECM.

Solution Methods for P1120 Code

Resolving a P1120 code typically involves addressing one or more of these common issues:

Replacing Throttle Position Sensor

If diagnostics indicate that the TPS is faulty:

• Disconnect battery power.
• Remove old TPS from its mounting location.
• Install new TPS and reconnect wiring.
• Reconnect battery and clear DTCs using an OBD-II scanner.

Repairing Wiring Issues

If damaged wiring is found:

• Identify and repair any frayed or corroded wires.
• Ensure all connectors are clean and secure.

Adjusting Throttle Body

If improper adjustment is suspected:

• Follow manufacturer guidelines for adjusting the throttle body.
• Perform necessary relearn procedures after adjustments.

Professional Assistance

If you are unable to resolve the issue after these steps:

• Seek help from a certified mechanic who can perform advanced diagnostics and repairs.

Cost Estimates for Repairs Related to P1120 Code

The cost associated with fixing a P1120 code can vary based on several factors including labor rates and parts availability:

• Throttle Position Sensor Replacement: $100 - $400 (parts and labor)
• Wiring Repairs: $50 - $200 depending on severity
• Throttle Body Adjustment/Replacement: $150 - $600 based on complexity

Professional diagnostics may incur additional costs ranging from $75 - $150.

Warnings and Recommendations

When dealing with a P1120 code:

• Immediate Attention Required: Ignoring this code can lead to further engine performance issues or damage.
• Avoid DIY Repairs Without Knowledge: If unsure about any step in diagnosing or repairing, consult with a professional mechanic.
• Use Quality Parts: Always opt for OEM parts when replacing components like TPS or throttle bodies to ensure compatibility and reliability.

Closing Paragraph

The P1120 trouble code indicates significant issues related to your vehicle's throttle position sensor, which can severely impact engine performance and drivability. By understanding its meanings, symptoms, and solutions, vehicle owners and DIY mechanics can effectively address this problem. Always prioritize safety by consulting professionals when necessary, especially if you encounter complex electrical issues or if repairs exceed your skill level.

Frequently Asked Questions About P1120

• What does P1120 mean?
  The P1120 code indicates that there is an issue with the throttle position sensor reporting an out-of-range signal.
• Can I drive my car with a P1120 code?
  It's not recommended as it can lead to reduced engine performance and potential safety risks.
• How do I fix a P1120 code?
  Fixing it typically involves inspecting and possibly replacing the throttle position sensor or repairing wiring issues.
• What are common symptoms of a P1120 code?
  Common symptoms include engine power loss, rough idling, harsh gear shifts, and activation of limp mode.
• Is it safe to ignore a P1120 code?
  No, ignoring this code can result in more severe engine problems over time.
• How much does it cost to repair a P1120?
  The cost can range from $100 - $600 depending on whether you need parts replaced or wiring repaired.
• Can I reset my check engine light after fixing P1120?
  Yes, you can reset it using an OBD-II scanner after repairs are made.
• Should I replace my throttle body if I get a P1120?
  Not necessarily; first diagnose if it's just the TPS or wiring issues before replacing more expensive components.