All about the throttle position sensor: purpose, malfunctions, repair
The throttle position sensor directly affects the operation of the engine. How to check it
What is the throttle position sensor responsible for?
The throttle position sensor (TPS) is a sensor that determines the current opening angle of the throttle valve and sends these readings to the control unit. It is one of the control elements of the injection engine control system .
Based on the readings of the throttle position sensor (not only, but also including), the control unit controls the speed, both at idle and under load. The TPS, along with other sensors (crankshaft position, detonation, mass air flow, etc.), are the “eyes” of the ECU, providing feedback when the gas pedal is pressed. On many modern engines, the TPS is also responsible for idle speed, since the electronic throttle replaces the classic idle speed regulator. For obvious reasons, the throttle position sensor is installed only on cars with an electronic fuel injection system.
How does a throttle position sensor work
The TPS is part of the throttle assembly, although it can be replaced separately. It is a potentiometer connected to the valve axis. When the valve moves during gas control (mechanically – with a cable, or a servomotor, if the gas is “electronic”), the potentiometer rotates by the same angle. Accordingly, its resistance changes, which gives feedback to the control unit – at what actual angle the valve is currently open. Based on this and other data from other sensors, the ECU corrects the mixture and regulates the speed in accordance with the embedded program.
Many modern TPS have a more reliable contactless circuit, where a Hall sensor is used instead of a potentiometer with resistive tracks.
Signs of a faulty throttle position sensor
As with almost any malfunction of a complex modern engine, the exact cause can only be determined with the help of an OBD scanner. However, there are two main signs that most likely indicate a malfunction of the throttle position sensor.
Let us once again stipulate that the listed symptoms may be a consequence of other malfunctions, but if the TPS is not working properly, they will certainly appear.
Checking the Throttle Position Sensor with a Multimeter
The method of self-testing the TPS using a multimeter is not suitable for all models, but in general cases it is possible and gives quite obvious diagnostic results. The algorithm of actions is as follows.
Method 1 – by Voltage
In this case, not only the extreme values are important, but also the smoothness of the voltage increase as you press the gas. The voltage change should occur smoothly and evenly, precisely corresponding to the manipulations with the pedal. If the initial or final voltage differs significantly from those indicated above, and there are also voltage surges that do not correspond to the pedal movements, the TPS is probably faulty. The most ideal option would be to conduct this test with an analog (pointer) voltmeter, for maximum clarity of readings, but today this is a rarity.
If the screen always shows “0”, then you should look for a break in the reference voltage to the sensor (there should always be 5 volts at the “A” and “B” terminals of the chip when the ignition is on).
Method 2 – by resistance
The resistance test of the TPS is carried out in a similar way. Only the multimeter is switched to the resistance measurement mode (limit – up to 20 kOhm), and the probes are connected to the signal and negative connectors of the sensor disconnected from the wiring. If the throttle has a mechanical drive, the TPS can be left in place and the throttle can be moved by hand. If it has an electric drive, the sensor must be removed and its axis rotated, for example, with a pencil.
When the pedal is released, the multimeter should show around 1-2 kOhm, when fully depressed – about 8-10 kOhm. If there are no values on the screen (it always shows one), there is a break in the sensor. If the values change stepwise, float, or differ greatly from the specified limits, the sensor is not working correctly.
Frequently asked questions
Can a car be driven if the throttle position sensor fails?
Yes. Despite the importance of the information coming from the TPS, the control unit is quite capable of maintaining relatively stable engine operation without it. But, of course, the driver will immediately feel the side effects: loss of idle stability, rev limitation, dives during acceleration, loss of power, etc.
Is it difficult to change the TPS yourself?
No. In the vast majority of cases, the throttle position sensor is located under the hood in easy access and is secured to the throttle body with a pair of bolts.
Is it possible to adjust or repair the throttle position sensor?
In general, no. The design and operation of the TPS does not imply any intervention other than the adaptation procedure (for some engines) using an OBD scanner. In practice, many craftsmen disassemble the case for the purpose of cleaning and even reconfiguring the potentiometer, but such examples are outside the scope of discussion of the standard functionality of the TPS.
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