Inspection Method
1)Accelerator Pedal Position Sensor
①Dismantle the wire harness plug and measure the two groups of angular potentiometer.One person presses the pedal slowly and the other person sees whether there is a gradual increase and decrease and whether there exists resistance jump.
②The accelerator pedal position sensor circuit and pin distribution are shown in Fig.4.8.Through measurement,the resistance value between pin 3#and 5#,and the resistance value between 2#and 6#are fixed value.The reference resistance value between pin 3#and 5#is 1.7 kΩ±0.8 kΩand reference resistance value between pin2#and 6#is 1.2 kΩ±0.4 kΩ.
Fig.4.8 Accelerator Pedal Position Sensor Circuit and Wire Harness Terminal
③Turn on the ignition switch,don’t start and don’t press the accelerator pedal.At this moment,the reference values for the output signal of accelerator position sensor are 0.72-0.74 V and 0.36-0.37 V respectively.
④Turn on the ignition switch,don’t start but press the accelerator pedal to the bottom.At this moment,the reference values for the output signal of accelerator position sensor are 4.61 and 2.32V respectively.
2)Electronic Throttle Body
①Dismantle the wire harness plug of electronic throttle body and then measure the resistance of the motor,which is usually between 1.5 Ωand 2.5 Ωunder normal temperature and won’t vary with the opening degree of valve plate.
②Dismantle the wire harness plug of electronic throttle body and its circuit diagram and terminal figure are shown in Fig.4.9.Measure the two groups of angular potentiometer.Open the valve plate slowly and there should be a gradual increase and decrease without any resistance jump.
③The sum of the resistance value between pin 2# and 5#,and the resistance value between 2#and 6#is constant value.The reference resistance value is 1.9 kΩ±0.2 kΩ.The resistance between pin 2#and 3#is constant value.
④Start the vehicle and the sum of voltages of pin 5#and 6#is about 5 V.
⑤Check whether the motor signal of the throttle is Mark-Space Ratio signal.
⑥Check whether there is a lot of carbon accumulation around the valve plate.If there is need for the elimination work of carbon accumulation,ensure the normal self-learning of electronic throttle.In the self-learning process of throttle,turn on the ignition switch and wait for 30 seconds.At this moment,there shouldn’t be any operation.
Note:(https://www.daowen.com)
Self-learning of electronic throttle body is needed after replacing ECU or electronic throttle body.
Fig.4.9 Electronic Throttle Body Circuit Diagram and Wire Harness Terminal
3)Intake Pressure Temperature Sensor
①Use the diagnostic unit to read the snapshot:when the vehicle is not started,intake pressure is close to 101kpa,and when started,the pressure declines to 30-40 kPa and the intake temperature is the environment temperature at that time;The pressure will decline when the accelerator pedal is pressed hard suddenly in neutral position.
②Check the temperature sensor:Dismantle the wire harness connector and then inspect the resistance between sensor’s pin 1# and 2#(circuit is shown in Fig.4.10)and the reference resistance at 20 °C is 2.5±5% kΩ,and the corresponding resistance values in other temperature can be measured by the characteristic curve in Fig.4.11.Simulation method can be used,for example,use the hair dryer to send hot wind to the sensor(not too close),and then the sensor’s resistance decreases.
Fig.4.10 Intake Pressure Temperature Sensor Circuit Diagram and Wire Harness Terminal
Fig.4.11 Characteristics Curve of Temperature Sensor
③Check the pressure sensor:Connect the wire harness plug,and under idling condition,the reference value of sensor signal voltage is around 1.3 V;under empty-load condition,open the throttle slowly,and the signal voltage doesn’t change much;open the throttle quickly,and the signal voltage increases instantly and then declines to around 1.5 V.
④Hypothesis method for quick inspection:under the idling and steady condition,unplug the wire harness connector of intake pressure sensor suddenly and judge whether there is obvious fluctuation of the engine’s rotation speed.If yes,it indicates that,basically,the single piece of intake pressure sensor works normally.
Note:
During the maintenance process,check whether the sensor’s vacuum channel is clogged and if yes,deal with it in time.When repairing,no high voltage gas is permitted to be used on the vacuum component;