Throttle Position Sensor

What is a throttle position sensor and where is it located?

An important part of the engine management system of your vehicle is the throttle position sensor, commonly abbreviated and referred to as a TPS sensor or switch. This sensor is usually mounted onto the side of the throttle body and is used to monitor the position of the plate inside the throttle body, i.e. how open or closed it is. The throttle body is one component of the fuel injection system; it is essentially a valve used to control the amount of air entering into the engine. The driver controls the position of this plate through the accelerator or gas pedal, either directly by cable or electronically, which is known as “drive by wire.” The more you press down on the accelerator pedal, the more this throttle plate opens, allowing for more air to enter the engine and thus the vehicle to go faster. Conversely, when you slow down, your throttle plate closes and the amount of air flowing into your engine is decreased.

The engine control unit / module (ECM, ECU, or PCM) uses the information that is sent to it from the throttle position sensor, along with input from other sensors, to calculate engine load and control many things such as fuel and ignition timing, as well as automatic transmission shift points. A properly functioning throttle position sensor (TPS) is crucial for the ECU to maintain good fuel efficiency and engine performance.

How do I know the throttle position sensor needs to be replaced?

If the throttle position switch (TPS) on your vehicle goes bad it could cause a poor / erratic running engine with little or no power. There are two major types of throttle position sensors used on vehicles today: contact type and non-contact type. Contact type (potentiometer) throttle position sensors are connected mechanically to the throttle body, and this type was once the industry standard. Many modern vehicles now use non-contact sensors, such as a Hall effect sensor. Although contact style throttle body sensors are more prone to failure, all throttle position sensors can fail over time. They are frequently exposed to high temperatures and vibration, and oftentimes the circuit board can crack and soldered connections can fail.

Faulty throttle body position sensors can lead to stalling, rough idle, poor performance, and fuel economy. Over time, contact style sensors may develop “dead spots”; this usually results in a hesitation under acceleration. You can check for dead spots by monitoring voltage output, watching for jumps or dips with either a scan tool or multi-meter. A multi-meter is also useful for checking the power supply and ground circuit, which will aid in locating the cause of the problem. Most TPS issues will be accompanied by a CEL, or check engine light and error code. Common OBDII Check Engine Codes related to throttle position sensors (TPS) include:

• P0120 Throttle Position Sensor/Switch A Circuit Malfunction
• P0121 Throttle Position Sensor/Switch A Circuit Range/Performance Problem
• P0122 Throttle Position Sensor/Switch A Circuit Low Input
• P0123 Throttle Position Sensor/Switch A Circuit High Input
• P0124 Throttle Position Sensor/Switch A Circuit Intermittent

Because the throttle position sensor is such a critical component of your car or truck, making sure that it is working properly is especially important. If your current TPS has failed, then a replacement should be obtained and installed as soon as possible.

Can I replace the throttle position sensor myself?

Replacing a faulty TPS can be easier than you think; it can be done on most applications with basic hand tools. Some applications may require fine adjustment of the new throttle position switch (TPS). A good repair manual will take you step by step through the process, which can range from vehicle to vehicle. Most likely, the air intake hose and possibly the serpentine belt will need to be removed to reach the sensor.