Pic. 2.244. Throttle position sensor
The throttle position sensor is shown in fig. 2.244.
The throttle position sensor is mounted on the side of the throttle body, the movable part of the sensor is connected to the throttle shaft. The sensor is made in the form of a variable resistor (potentiometer), the resistance of which varies depending on the position of the throttle. When the damper is opened, the resistance of the sensor decreases, and when it is closed, it increases. The engine control unit supplies the sensor with a reference voltage and measures the voltage in the sensor signal circuit. The ECU uses information from the throttle position sensor to control the ignition timing and fuel injection duration. Based on the signals from the throttle position sensor and the mass air flow sensor, the ECU calculates the engine load.
Pic. 2.245. Connection diagram for throttle position sensor with ECU
Conditions for storing fault codes
The ECU memorizes P0121 and turns on the engine management system malfunction indicator lamp in the event of a mismatch between the engine load signal from the throttle position sensor and the signal from the absolute pressure sensor. This code indicates that the throttle position and air flow information provided to the ECU by the throttle position sensor and the absolute pressure sensor does not correspond to the actual engine load.
The ECU stores code P0122 and turns on the engine management system malfunction indicator lamp if the throttle opening angle is less than 2.1°for more than 0.2 seconds in two driving cycles. This code indicates that the throttle position sensor or ECU is detecting an unusually small throttle opening angle. The ECU memorizes code P0123 and turns on the engine management system malfunction indicator lamp if the throttle opening angle is greater than 105.4°for 0.2 s in two driving cycles. This code indicates that the throttle position sensor or ECU is detecting an unusually large throttle opening angle.
Note. The nominal resistance value when measured at terminals 1 and 3 of the throttle position sensor is in the range of 1600–2500 ohms.
Examination
Disconnect the throttle position sensor electrical connector.
Pic. 2.246. Connection diagram when checking the throttle position sensor
Check resistance on terminals 2 («weight» sensor) and 3 (sensor power supply) sensor electrical connector (pic. 2.246).
Rated resistance value: 0.7-3.0 kΩ
Connect an analog ohmmeter to pin 2 («weight» sensor) and 1 (sensor signal) sensor electrical connector.
Slowly moving the throttle valve from idle to full open position, watch for a smooth change in resistance in proportion to the throttle opening angle.
If the resistance deviates from the norm or changes unevenly, replace the throttle position sensor.
Throttle position sensor tightening torque: 1.5–2.5 Nm.