P0120 – Throttle Position Sensor Circuit Malfunction

Welcome to our article on the P0120 code, which refers to a Throttle Position Sensor Circuit Malfunction. The Throttle Position Sensor (TPS) is a crucial component that detects the position of the throttle blade and sends a signal to the PCM. When the voltage from the TPS circuit A goes outside the specified range or is inconsistent with TPS circuit B, the P0120 code is triggered.

This code can cause various symptoms, including poor idle quality, misfiring, starting or stalling issues, and the illumination of the Malfunction Indicator Lamp (MIL). If you have encountered the P0120 code, it is important to understand its technical description, meaning, severity, common causes, and troubleshooting steps for repair.

Key Takeaways:

• The P0120 code indicates a Throttle Position Sensor Circuit Malfunction.
• The TPS is a potentiometer that detects the angle of the throttle blade.
• Symptoms of a P0120 code include poor idle quality, misfiring, and starting or stalling issues.
• The potential causes of the code include a faulty TPS, corrosion in the MAP or TPS connector, and a misrouted harness causing chafing.
• Troubleshooting steps may involve checking TPS voltage, inspecting the TPS connector and wiring, and replacing the TPS if necessary.

Symptoms of a P0120 Code

When your vehicle’s onboard diagnostics system detects a P0120 code, it signifies a Throttle Position Sensor/Switch (TPS) Circuit Malfunction. Understanding the symptoms associated with this diagnostic trouble code (DTC) can help you identify and address the issue promptly. The symptoms of a P0120 code can vary depending on the specific vehicle and its manufacturer’s failsafe mode strategy. Some common symptoms include:

1. Malfunction Indicator Lamp (MIL) Illumination: The check engine light or MIL on your dashboard may illuminate, indicating a potential issue with the throttle position sensor circuit.
2. Misfiring: Your vehicle may experience misfires, which can occur either at idle or during highway speeds. This can result in engine hesitation or a noticeable lack of power.
3. Poor Idle Quality: The engine’s idle may become rough or unstable, leading to a noticeable vibration or shaking sensation.
4. Engine Not Idling: In some cases, the engine may fail to idle altogether, making it difficult to keep the vehicle running at a stop.
5. Starting and Stalling Issues: You may encounter difficulties starting the engine, or the engine may start but then stall shortly after.

It’s important to note that the presence of these symptoms does not guarantee a P0120 code. Consult a professional mechanic or utilize a reliable scan tool to accurately diagnose the cause of the symptoms and confirm the specific DTC present in your vehicle.

Dealing with a P0120 code promptly is crucial to prevent further damage to your vehicle’s engine and drivability. In the next section, we will explore the potential causes of a P0120 code to help you with troubleshooting and repairs.

Causes of a P0120 Code

The P0120 code can be triggered by various causes related to the Throttle Position Sensor (TPS) A Circuit malfunction. Identifying and addressing these causes is crucial for resolving the issue.

1. Sticking Throttle Return Spring: A sticking throttle return spring can prevent the throttle blade from returning to its closed position properly, causing the TPS circuit A voltage to go outside the normal operating range.
2. MAP or TPS Connector Corrosion: Corrosion in the Manifold Absolute Pressure (MAP) or TPS connector can disrupt the electrical connection, leading to inconsistent voltage readings and triggering the P0120 code.
3. Misrouted Harness: A misrouted harness can cause chafing and damage to the wiring, affecting the TPS circuit A signal. This can result in the P0120 code being activated.
4. Faulty TPS: A faulty Throttle Position Sensor can provide inaccurate voltage signals to the PCM, causing the TPS circuit A voltage to deviate from the expected range and triggering the P0120 code.
5. Faulty PCM: A malfunctioning Powertrain Control Module (PCM) can also contribute to the P0120 code by generating incorrect signals or failing to interpret the TPS circuit A voltage properly.

These causes can disrupt the normal operation of the TPS circuit A and result in the P0120 code being stored in the system.

Quote:

“Identifying the specific cause of the P0120 code is essential for effective troubleshooting and repair. By addressing the underlying issue, you can ensure the proper functioning of the Throttle Position Sensor circuit and prevent potential performance and drivability concerns.”

Understanding the causes of the P0120 code can help guide the diagnostic process and determine the most appropriate repair steps. Let’s move forward to the next section to explore the troubleshooting procedures for the P0120 code.

Troubleshooting a P0120 Code

To effectively troubleshoot a P0120 code, it is important to follow a systematic approach that includes the use of a scan tool, checking the TPS voltage, inspecting the TPS connector and wiring, and manipulating the TPS wiring harness if necessary. Here are the troubleshooting steps to help you diagnose and resolve the issue:

1. 1. Step 1: Use a scan tool to observe the TPS voltage

Start by connecting a scan tool to your vehicle’s OBD-II port and accessing the live data. With the Key On Engine Off (KOEO), monitor the voltage of TPS circuit A. The voltage should be approximately 0.45 volts when the throttle is closed and should gradually increase to around 4.5 to 5 volts as the throttle is depressed. If the TPS voltage doesn’t follow this expected pattern or shows any glitches, it may indicate a faulty TPS.

1. 1. Step 2: Check the TPS connector and wiring

Inspect the TPS connector and wiring for any signs of damage, corrosion, or loose connections. Ensure that there is a good ground at the TPS connector and also check for the presence of the 5 volts reference voltage. Any issues with the TPS connector or wiring can result in improper TPS readings and trigger the P0120 code.

1. 1. Step 3: Verify continuity in the TPS signal circuit

To check for continuity in the TPS signal circuit, you can jump a fused wire between the ground circuit and the signal circuit of the TPS connector. If the TPS reading still doesn’t change to zero or shows erratic behavior, it may indicate an open or short in the signal wire, or even a faulty PCM (Powertrain Control Module).

1. 1. Step 4: Manipulate the TPS wiring harness

Manipulating the TPS wiring harness while monitoring the TPS readings can help identify any intermittent issues or a bad TPS. Sometimes, a change in idle caused by manipulating the wiring harness can indicate a faulty TPS that needs to be replaced.

It is important to note that some TPS sensors may require fine adjustment. If you are unsure about adjusting the TPS or if the issue persists even after troubleshooting, it is recommended to seek professional assistance. Proper diagnosis and repair are essential to resolve the issues associated with the P0120 code and ensure optimal performance of your vehicle.

Other TPS Sensor and Circuit Related DTCs

When diagnosing Throttle Position Sensor (TPS) issues, it’s important to be aware of other related Diagnostic Trouble Codes (DTCs) that may occur. Here are some additional codes to keep in mind:

• P0121: TPS “A” Circuit Range/Performance
• P0122: TPS “A” Circuit Low Input
• P0123: TPS “A” Circuit High Input
• P0124: TPS “A” Circuit Intermittent

These codes indicate different issues with the Throttle Position Sensor and its circuit. Each code provides valuable information to help pinpoint the source of the problem. Proper diagnosis and appropriate repairs can resolve these issues effectively.

DTC Code Comparison

Here’s a concise comparison of the TPS-related DTCs mentioned above:

By comparing and understanding the specific DTCs, you can better diagnose and address issues related to the TPS and its circuit.

Suggestions for Repairing a P0120 Code

If you are experiencing a P0120 code indicating a Throttle Position Sensor Circuit Malfunction, there are several suggestions you can follow to address the issue:

1. Replace the faulty TPS if necessary: Assess the condition of the Throttle Position Sensor (TPS) and replace it if it is determined to be faulty. This component plays a crucial role in detecting the angle of the throttle blade and sending the corresponding signal to the Powertrain Control Module (PCM).
2. Ensure proper sensor adjustment if required: Some TPS sensors may require fine adjustment to accurately detect the throttle position. Refer to the vehicle’s manufacturer guidelines or consult a professional for guidance on adjusting the sensor accordingly.
3. Seek professional assistance if unsure or uncomfortable with the process: If you lack the necessary expertise or are unsure about performing the repairs yourself, it is advisable to seek professional assistance. A qualified technician can diagnose the issue accurately and carry out the necessary repairs with precision.

Remember, proper diagnosis and repair are essential in resolving the issues associated with the P0120 code. By following these suggestions, you can ensure the effective repair of your vehicle’s Throttle Position Sensor Circuit.

Conclusion

In conclusion, the P0120 code indicates a Throttle Position Sensor/Switch (TPS) A Circuit Malfunction. This code can cause various symptoms such as MIL illumination, misfiring, poor idle quality, and starting or stalling issues. The potential causes of this code include a sticking throttle return spring, corrosion in the MAP or TPS connector, misrouted harness causing chafing, a faulty TPS, or a faulty PCM.

To diagnose and resolve the issues associated with the P0120 code, it is important to follow proper troubleshooting steps. This may involve using a scan tool to check the TPS voltage, inspecting the TPS connector and wiring, and potentially replacing the TPS if necessary. Other related codes to be aware of are P0121, P0122, P0123, and P0124.

If you are unsure or uncomfortable with the repair process, it is recommended to seek professional assistance. A skilled technician can accurately diagnose the issue and ensure efficient repairs, ultimately resolving the problems caused by the P0120 code.