P CODES (POWERTRAIN) P0100 - P0199 P0120

    Troubleshooting P0120 Code - ETS Main Throttle Position Sensor Malfunction


    The P0120 code indicates that the Engine Control Module (ECM) has detected a malfunction in the Electronic Throttle System (ETS) Main Throttle Position Sensor. This sensor is responsible for measuring the position of the throttle valve and sending that information to the ECM. If the sensor is malfunctioning, it can cause issues with engine performance and drivability. In this guide, we will discuss what the P0120 code means and provide step-by-step instructions on how to troubleshoot and fix the problem.

    Step 1: Understand the Electronic Throttle System

    The Electronic Throttle System (ETS) is a modern technology that has replaced traditional mechanical throttle linkages with electronic sensors and actuators. The ETS uses sensors to measure the position of the throttle valve and sends that information to the Engine Control Module (ECM), which adjusts the throttle opening accordingly. Understanding how the ETS works is essential to troubleshooting the P0120 code.

    Step 2: Check the Throttle Position Sensor Wiring

    The first step in troubleshooting the P0120 code is to check the wiring and connectors of the Throttle Position Sensor. Make sure that the wiring is not damaged, corroded, or disconnected. Inspect the connectors for any signs of damage or corrosion. If the wiring and connectors appear to be in good condition, move on to the next step.

    Step 3: Test the Throttle Position Sensor

    The next step is to test the Throttle Position Sensor itself. To do this, you will need a multimeter. Disconnect the wiring connector from the sensor and set your multimeter to measure voltage. Turn on the ignition switch but do not start the engine. Place the red probe of your multimeter on the signal wire of the sensor, and the black probe on a good ground. Slowly open and close the throttle valve while monitoring the multimeter reading. The voltage should increase smoothly as you open the throttle and decrease smoothly as you close the throttle. If the voltage reading is erratic or does not change smoothly, replace the Throttle Position Sensor.

    Step 4: Check the Throttle Body

    If the Throttle Position Sensor is functioning correctly, the next step is to check the Throttle Body itself. Make sure that the Throttle Body is clean and free of any debris or obstructions. Check for any signs of wear or damage, such as cracks or broken parts. If the Throttle Body is damaged or worn, replace it.

    Step 5: Check for Vacuum Leaks

    If the Throttle Body is functioning correctly, the next step is to check for any vacuum leaks. Vacuum leaks can cause issues with the ETS and affect the performance of the Throttle Position Sensor. Check all vacuum hoses and connections for any signs of damage, wear, or leaks. Replace any damaged or worn hoses and ensure all connections are secure.

    Step 6: Check the Engine Control Module

    If all of the above steps have been completed, and the problem still persists, it is time to check the Engine Control Module (ECM). A malfunctioning ECM can send incorrect signals to the Throttle Position Sensor, which can result in the P0120 code. Have the ECM scanned and diagnosed by a qualified mechanic. If necessary, replace the ECM.


    Troubleshooting the P0120 code requires a step-by-step approach, starting with checking the Throttle Position Sensor wiring and connectors, and testing the sensor itself. If the Throttle Position Sensor is functioning correctly, check the Throttle Body and vacuum hoses for any issues. If the problem still persists, check the Engine Control Module. By following these steps, you can fix the problem and ensure that your engine is running smoothly.

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