TTEC4848 Vehicle Electronic Controls- blog 1 off car

Engine Electronic Control Systems--Sensors

off car check

TPS - Throttle Position Sensor(potentiometer) or Throttle Position Switch

Function: is to supply information to the ECU about the position of the car's throttle.

Malfunctioning of a TPS can result in improper data being fed to the ECU, which monitors engine performance, in respect to the fuel efficiency of the car.

How to check a Throttle Position Sensor?

1.we have to know the meaning of each pin: Vcc(power supply from ECU), E2(ground), VTA(the signal go back to ECU), IDL(throttle position of Ideal speed )

2.we use voltmeter to check the voltage of the throttle position angle

CTS (Coolant Temperature Sensor)

THW (Thermistor Water)

ECT (Engine Coolant Temperature)

We checked the thermistor of water first we know it will be control the engine coolant system, when the temperature change than it change the ohms so the signal voltage has change. Than told to ECU which temperature does engine have and also it can switch on/off the fan to coolant engine.

Experiment:

We put the thermistor into water and heat the water and check the temperature with a thermometer and use the ohmmeter measure the resistance between the terminals.

The manufacturer's specifications

Temperature             Resistance

(deg C)                 (ohms)

     -10                7,000-12,000

      20                 2,000-3,000

      50                   700-1,000

    80                   200-400

       85+               Less than 200

Data from my experiment

Water temperature           Resistance

   (deg C)                   (ohms)

     20                      2,500

     30                      1,760

     40                      1,250

    50                       880

    60                       600

    70                       450

    80                       330

    90                       185

we can see the experiment data follow the manufacturer's specifications, and proved the water temperature changed the thermistor resistance.

Experiment - Oxygen sensor circuit

Oxygen sensor circuit diagram

Components list:
Zener Diode: D1 = 9V1 IzRm 5.6mA
Diodes: D2/D3/D4=1N4001 Diode,Max Pd=2.5W,Max I=1A@75^OC, MAX reverse voltage=100V.
LED: red/yellow/green=1.8V 9.5mA
Resistors: R2/3/4  =  1K Ω
               R5        = 410Ω
               R6        = 10KΩ
               R7        = 271Ω
               R8        = 470Ω
Capacitors: C1&C2= 0.1uF
Op-Amp = LM324


Calculations


From diagram we know R6=10K and power supply is 12V,also we know from signal power supply is 0-1V. On the diagram we can see the voltage drop between R6 and R8 is 0.63V, the voltage drop between R8 and R7 is 0.23V.
So we can use these information to calculate:


R5=Vs-Vd2-Vd1/IzRm
  =12V-0.6V-9.1V/0.0056A
  =2.3V/0.0056A
  =410Ω


R8=V8/I=0.63V-0.23V/((Vd1-0.63)/R6)
  =0.4V/((9.1V-063V)/10000Ω)
  =0.4V/0.00847A
  =472.25Ω


R7=V7/I
  =0.23V/.000847A
  =271.54Ω


R2/R4=Vs-Vd2-Vled/Iled
     =12V-0.6V-1.8V/0.0095A
     =9.6V/0.0095A
     =1010.52Ω


R3=Vs-Vd2-Vd4-Vled5/Iled
  =12V-0.6V-0.6V-1.8V/0.0095A
  =9V/0.0095A
  =947.36Ω

Oxygen sensor circuit test on a bread board

From this test I found a big problem with my Operational Amplifier. When I built this circuit than use a power supply machine which supply 12V power and a voltage limit machine which can change voltage between 0-1Volt supply to the signal(sensor input). When I test my circuit I saw only the yellow LED could turn on and when I change the power supply of signal from 0-1volt the other two LED didn't bright, than I checked the circuit, it connect well also I use multimeter to test each components, I couldn't find any problem with them. Than I asked tutor, he said connect power supply and test each pin of Op-Amp. I did it, and found some pins reading were incorrect. So I change an Op-Amp, than my circuit works very well.

Those reading from my test I changed the signal power supply between 0-1volt and I can see the different LED was bright also I can read the available voltage change from the pins of an Op-Amp. It tell us how did these components work, with a vehicle the yellow LED bright is mean normal condition above 14.7:1, when the red LED bright is mean rich condition O2-less but fuel-much, when the green LED bright is mean lean condition O2-much but fuel-less.

On the other hand I checked current flow of D1=4.9mA, between R6 and R8 above 0.847A, after R7 above 0.88A, and before the three LEDs above 8.5mA. All of these measurment same as datasheet and calculations.

Than I am going to sold my real circuit...

This is my real circuit, now it works very well. But before when I test it, it got a problem. When I connect power supply and change the signal power supply between 0-1volt the yellow LED bright, when the green LED or red LED turn on or turn off so I use multimeter to check available voltage of the yellow LED circuit, and when I checked D3 and I couldn't get reading from component side but I can get reading from soldering side, than I told to tutor he said this called "dry welding" is mean we can see the welding is very well but the pin doesn't connect to the solder, so it doesn't connect the circuit.

Real circuit test on engine

From these to videos we can see when we switch on an engine and use this circuit to test Oxygen sensor and use multimeter to check the sensor's available voltage we can know how does Oxygen sensor works and when the Oxygen sensor change condition it told to the ECU, than the ECU will be supply more oxygen or more fuel into engine make this balance.