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Throttle position sensor

Throttle position sensor

1. Functions and duties of throttle position sensor

Throttle position sensor is used to measure the open position of the throttle to report to the ECU. From there, the ECU will use the information signal sent by the throttle position sensor to adjust the fuel injection time, cut off the fuel, early ignition control, adjust the idle compensation and shift control..

When the accelerator pedal is in full load mode, the ECM will automatically disconnect the A/C, the ECU will switch to the “Open loop” mode to control fuel injection, ignoring the signal from the oxygen sensor (see picture 1)


Throttle position sensor


2. Structure of the throttle position sensor

The structure of the throttle position sensor is quite simple, we can distinguish them according to each vehicle model according to the following signs:

– Throttle position sensor for old engine model uses 2 contacts IDL and PSW.

Throttle position sensor 1


– The higher generation type uses a linear circuit (with resistors) and still has IDL contacts.

Throttle position sensor2


– New generations of engines using electronic throttle will have 2 throttle sensor signals to increase reliability, and the throttle position sensor will no longer use a resistor linear circuit, but use Hall to increase durability.

Throttle position sensor


3. Working principle of throttle position sensor

– Throttle position sensor contact type: the sensor has 2 contacts IDL and PSW, When the throttle is in the non-depress the gas pedal, the IDL is connected to the E2 pin to report to the ECU, the ECU will detects that it is in idling mode to compensate fuel and control fuel injection in idling mode, when the throttle is over 50%, the PSW will connect to the E2 and the ECU will recognize that it is opening the throttle (in full load mode), the ECU will adjust the amount of fuel to increase engine power.

– Linear type + contact: Includes 4 pins (+, -, signal, IDLE).

– Linear type (like a rheostat): The sensor is powered by Vc (5V) and ground, composed of 1 resistor circuit and 1 scanning blade on that resistor circuit, when the axis of the butterfly blade rotates (opens and closes the butterfly) will cause the blade to change position on the resistor circuit, so changing the output voltage (signal pin)

– Hall type (new generation): The throttle position sensor has 2 signals, the voltage of the sensor also changes according to the throttle opening but based on the Hall effect principle (there are 2 types):

* Forward type: 2 signals increase and decrease together.

Throttle position sensor


* Reverse type: 1 signal increase 1 signal decrease.

Throttle position sensor


4. Throttle position sensor specifications

The signal transmitted to the ECM of the throttle position sensor is in the form of a voltage, this voltage will change according to the throttle opening. Depending on the design, the TPS has one or two signals sent to the ECM and with or without IDL switch

– Signal voltage at no load is 0.5-0.8V, when depress on the accelerator the voltage will gradually increase up to 4.5V.

5. Circuit diagram of throttle position sensor

On the electronic throttle position sensor, there is usually an additional throttle control motor (2 wires).

Throttle position sensor


6. Position of the throttle position sensor

Located on the throttle assembly

Throttle position sensor

7. How to test the throttle position sensor

– With old engine model, still use 2 contacts type:

Check if the IDL contact when the throttle at closed position is connected to the E2 pin?, when slightly depress on accelerator, the IDL must be disconnected from the E2. Check if the PSW when the throttle is open more than 50% is connected to the E2?, when the throttle is released back, the PSWmust separate from the E2.

– With linear and Hall sensor types:

Unplug the power connector, check the sensor pin has 5V Vc, Ground and signal pin. When changing the throttle valve opening, the voltage value at the Signal pin must change linearly and without interruption at any point.

Throttle position sensor


8. Common failures of the throttle position sensor

– Sensor damaged due to wear of the resistance circuit. Or damaged IC Hall

– Broken wire

– Signal wire touches positive, touches ground

– loose connector

– Damage to the ECU also report an error of the throttle position sensor

In case the signal from TPS is abnormal, the engine may have the following symthom: unstable idling speed, poor acceleration, increased fuel consumption, high concentration of CO, HC in exhaust gas

9. Practical experience when checking throttle position sensor

– Contact type (older model): improperly operate of the contact (when the IDLE contactor does not disconnect from E2, the throttle is hit).

– With cars using electronic throttle, when the throttle position sensor signal is lost, it is often impossible to increase the RPM, if can, it is limited to RPM.

– Some older models of cars, the throttle position sensor can be rotated and adjusted to a small angle through the screw slot, it is not recommended to adjust the throttle position sensor signal too high or too low, it will affect the control idle speed.

10. Check the throttle sensor through the diagnostic tools

Use the Data Analysis (Data List) function to check if the signal of the throttle sensor is good.

Throttle position sensor


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