Detailed explanation of automobile engine technology throttle position sensor

1. Function, classification and identification of throttle position sensor

(1) Function

The throttle position sensor is one of the most important sensors in the automotive electronic control system. It is mainly used in the engine electronic fuel injection system and the electronically controlled automatic transmission system. The throttle position sensor is installed at one end of the throttle shaft on the throttle body to detect or monitor the size and speed of the throttle opening, and convert the position signal into an electrical signal and input it into the electronic control unit. It is used to determine various working conditions of the engine, thereby controlling different injection quantities and ignition timing. In cars equipped with electronically controlled automatic transmissions, the throttle position sensor signal is the main signal when the transmission shifts and the torque converter locks.

(2) Type of throttle position sensor

The throttle position sensor equipped with the traditional cable-controlled throttle valve is divided into contact switch type, sliding resistor type, and integrated type integrating idle switch and sliding resistor according to the overall structure. The throttle position sensor used in the new intelligent electronic throttle shaft control system is commonly divided into two types: dual sliding resistor type and linear dual Hall type.

At present, the throttle position sensors mainly used in engine electronic control systems are Hall element type and dual sliding resistor type. Toyota Camry, Corolla, etc. use Hall element type; Nissan Teana and GM Excelle use dual sliding resistor type.

2. Hall type throttle position sensor

(1) Structural principle and installation location

The 2016 Toyota Camry Hybrid (engine model 6AR-FSE) uses a non-contact dual Hall element throttle position sensor, the structure of which is shown in the figure below. It mainly consists of a Hall element and a magnet, where the magnet is installed on the throttle shaft and can rotate around the Hall element.

The control circuit and signal output characteristics of the Hall throttle position sensor are shown in the figure above. When the throttle opening changes, the magnet rotates accordingly, thereby changing the relative position between the magnet and the Hall element. The Hall IC is surrounded by a magnetic yoke. The Hall IC converts the change in magnetic flux into an electrical signal and outputs it to the ECM in the form of a throttle position signal.

The throttle position sensor has two sensor circuits: VTA1 and VTA2, each emitting a signal. VTA1 is used to detect the throttle opening, and VTA2 is used to detect a fault in VTA1. The sensor signal voltage is proportional to the throttle opening, varies between 0 and 5V, and is transmitted to the ECM terminals VTA1 and VTA2.

When the throttle is closed, the sensor output voltage decreases; when the throttle is opened, the sensor output voltage increases. The ECM calculates the throttle opening based on these signals and controls the throttle actuator to respond to the driver's input. These signals are also used to calculate the air-fuel ratio correction value, power boost correction value and fuel cut control.

(2) Circuit connection

The 2016 Toyota Camry Hybrid throttle position sensor circuit is shown in the figure below.

The throttle position sensor is integrated in the throttle body assembly E16. E16 has 6 pins. Pins 1 and 2 are the throttle actuator motor control ports. Pins 6 and 4 output throttle position signals VTA1 and VTA2 to 122# and 88# of the engine control unit port E81 (F) respectively. Pin 5 is the VCTA 5V reference voltage provided by the engine control unit 121#; Pin 3 is grounded through the engine control unit 120#.

(3) Detection

① Check the sensor power supply: Disconnect the throttle body connector E16, and use a multimeter to measure the voltage between E16/5 and E16/3, which should be 4.5~5.5V. Otherwise, check the ECU power supply circuit. If the ECU power supply circuit is normal, replace the ECU.

② Check the signal voltage of the sensor: Connect the fault diagnosis instrument, turn on the ignition switch, step on the accelerator pedal, and read the throttle position sensor data VTA1 and VTA2 readings. The values ​​should conform to the table below.

③ Check the sensor harness and connectors: Disconnect the throttle body connector E16 and the engine control unit ECM connector E81, and check the resistance between the connectors or between the connector and the vehicle body ground as shown in the table below. The resistance value should meet the requirements shown in the table. If not, replace or check the harness.

3. Sliding resistor throttle position sensor

(1) Structure

Sliding resistor throttle position sensor, also known as linear output throttle position sensor, variable resistor throttle position sensor, potentiometer throttle position sensor. Currently, dual variable resistor throttle position sensor is being widely used in automobiles.

The sliding resistor throttle position sensor is a three-wire sensor, in which two pins are at both ends of the resistor and are used as power terminals and ground terminals to provide 5V voltage from the engine ECU, and the third pin is connected to the sliding contact. The throttle shaft is linked to the contact (or contact). When the throttle rotates, the sliding contact can move on the resistor, causing the change in the sliding contact potential. The throttle position signal is converted into a voltage value using the change in resistance, as shown in the figure below. Because this voltage changes linearly, it is also called a linear output throttle position sensor. Based on this linear voltage value, the ECU can sense the opening of the throttle and make corrections to the injection amount.

(2) Sensor detection

The 2013 Buick Excelle throttle position sensor circuit is shown below. The engine control module provides a 5V reference voltage circuit to the throttle position sensor and provides ground to the low reference voltage circuit. The signal voltage provided by the throttle position sensor changes with the throttle opening. The throttle position sensor signal voltage is less than 0.5V when idling. The throttle position sensor voltage is generally close to 0V when idling, but may be as high as 0.5V. At wide open throttle (WOT), the throttle position sensor voltage should increase to more than 4V.

The throttle position sensor is detected as follows:

① Turn off the ignition switch and disconnect the wiring harness connector on the throttle body assembly.

② Measure the resistance between the 5V reference terminal 2# and the low voltage reference terminal 1# of the throttle position sensor to see if it is between 5.0 and 5.3 kΩ. If the resistance is not within the specified range, replace the throttle body assembly.

③ Measure the resistance between the throttle body assembly signal terminal 3# and the low voltage reference terminal 1#. Test the throttle sensor in the full range. The resistance should vary between 2.5 and 6.8 kΩ without any peaks or valleys. If the resistance is not within the specified range or is unstable, replace the throttle body assembly.

④ Connect the applicable terminal of the throttle sensor with 5V voltage and ground, and test the voltage between the signal terminal and the low voltage reference terminal. Test the throttle sensor in the full range. The voltage should fluctuate between 0.6 and 4.7V without any peaks or valleys. If the voltage is not within the specified range or is unstable, replace the throttle body assembly.

(3) Dual variable resistor throttle position sensor

The two sensors in the dual variable resistor throttle position sensor are usually installed in combination. When one sensor fails, it can be identified in time, which increases the reliability of the system. From the change relationship of the output signals of the two sensors, there are two types: anti-phase type and in-phase type. The in-phase type can be divided into two types: linear change with the same slope and linear change with different slopes.

The structure and internal circuit of BOSCH's dual variable resistor throttle position sensor are shown in the figure below.

The dual-track throttle position sensor on the throttle shaft is used to monitor the accurate opening of the throttle. The slide of the throttle position sensor (two potentiometers) is coaxial with the throttle. When the throttle rotates, the potentiometer slide rotates synchronously. When the 5V working voltage is applied, the changing resistance is converted into a voltage output signal. The output voltage of the potentiometer changes with the position of the throttle, allowing the control unit to accurately know the opening of the throttle. Since the two potentiometers are installed in reverse phase, when the throttle position changes, the voltage of the two signals changes linearly, one increases and the other decreases at the same time. The figure below shows the output characteristics of the throttle position sensor of Nissan cars.

The dual variable resistor sensor circuit of Nissan Teana series is shown in the figure below.

The engine control unit ECM provides a 5V reference voltage to the sensor 1# terminal through the 72# terminal; the sensor 4# terminal is grounded through the 36# terminal of the electronic control unit. The sensor 2# and 3# terminals output TPS1 and TPS2 throttle position signals, which are sent to the 33# and 36# terminals of the engine control system respectively.

The inspection of the dual variable resistor throttle position sensor (taking Nissan Teana as an example) is as follows:

Turn on the ignition switch, shift the shift lever to D gear (A/T) or 1 gear (M/T), and use the voltage range of the multimeter to check the voltage between ECM port 33 (signal of throttle position sensor 1# end) and 34 (signal of throttle position sensor 2# end) and ground when the accelerator pedal is in different states. The inspection results should meet the requirements in the following table. If not, replace the throttle body assembly.