SENSORS (Off Car)

Throttle Position Seneor (TPS)

What type of TPS is this ?

 Linear.

Explain its internal operation and why your voltage changes.

The linear TPS has a variable resistor (potentionometer) which has a slide contact that moves across the resistor when the throttle butterfly moves. This gives a voltage of 0.5-1v when butterfly is closed at idle and then voltage increases as throttle buttefly opens to aprox. 4.5-5v at fully open.

Now connect a power supply to your sensor and test the voltage output at diffrent throttle angles.

Throttle angle :                                          Voltage output :

  fully closed 0°                                                      0.9v
        30°                                                                1.59v
        45°                                                                2.14v
        65°                                                                2.95v
        80°                                                                3.92v
  fully open 90°                                                      4.8v

TPS Throttle Position Switch

Place the ohm meter across the E and IDL pins and with throttle shut, check for continuity.

E - IDL throttle shut = 0.1Ω throttle open = 0.L

Place the ohm meter across the E - PSW pins and check for continuity when throttle is wide open.

E - PSW throttle open =  0.2Ω throttle closed = 0.L

Explain the internal operation of this sensor and why the resistance changes.

The resistance changes because the TPS switch has contacts that switch so at closed throttle you can maessure E - IDL resistance. but when contacts open you get 0.L the same thing happens with E - WOT with contacts closed you can meassure resistance but when they open you get 0.L

AIR FLOW/MASS SENOR (MAF)

What voltage did you get when you first powerd up the sensor without passing air over the sensor?

1.1 volt

How did the voltage change when air was passed over the sensor?

The voltage increased from 1.1v to 3.2v

Explain the internal operation of this sensor.

The (MAF) sensor has a power transistor that supplies voltage to a wheat-stone bridge. This has two temperature sensitive resistors one is a PTC and acts as a heating element the other is NTC resistor and acts as a thermistor, each is connected to another resistor. The PTC has a platinum hot wire and is connected to the inverting side of a differential op-amp and also sends signal to ECU. The thermistor is connected to the non-inverting side of the differential op-amp. When engine speed increases air flow increases cooling the thermistor and lowering its resistance this increases the voltage across the second resistor which suppiles the non-inverting side of the op-amp. This increases the voltage output of the op-amp which turns the power transistor more on so more current is supplied to thermistor heating it back up. The higher current is also supplied to the PTC resistor which sends an increased signal to the ECU.

Vane or flap airflow sensor/meter (AMF)

http://www.youtube.com/watch?v=cVDdOoHj-_I

Explain the internal operation and why your voltage changes.

The vane/flap is L shaped plate that has a measuring plate and a copmensating plate attached to a return spring. The incoming air deflects the mearsuing plate in proportion to the volume of intake air flow. The compensating plate moves in the damping chamber and prevents rapid movement of the measuring plate. The measuring plate is connected to a potentiometer which coverts movement of the measuring plate into a veriable voltage signal. A moveable contact on the measuring plate move across a fixed resistor that has a 5v referance voltage and a ground, as air intake increases the output voltage signal changes as the moveable contact moves across the fixed resistor. On the sensor we tested the voltage went from a higher voltage 4.53v at closed to a lower 0.45v at open.

Knock Sensor :

Connect the knock sensor up to an oscilloscope. Tap the end of the knock sensor and observe the wave form.

Explain why we are reading a voltage from this sensor when we are not supplying a voltage to it.

This is because the knock sensor has a piezo crystal element. When the element is destorted by vibration from the cylinder block caused by detonation it produces a small AC voltage.