blog 2 INPUT SENSORS AND ACTUATORS ON CAR

There is alot of sensors and actuators in a car more in some than in others but all of them mostly inportant if one is faulty it will be noticed by driver some differint ways than others could be by performance economical alot of different ways.I pack probed a fuel injector with a pin and got a voltage reading of 14.1v.It is important to get a good voltage at the injector because if there is a bad voltage then that injector wont work properly and car will lack performance and could have bad fuel economy because ecu will be makin richer addin fuel to make it run right.A bad voltage could be cause by a bad earth or resistance build up in control circuit.
I was asked to draw a diagram of the fuel injectors.

Refrence voltage at TPS
The reason for the reference voltage at the TPS is to let the ECU know wat is happening how open throttle is so ecu knows how much fuel to add.Thing like bad earth and open circuit is things that could cause the reference voltage to be low.
To check the earth at TPS I had to back probe the ground wire wiv a pin and record voltage. I did this and got a result of 0.03v,this shows that there is a good earth.
I got an input wire again I back probed the wire i recorded the voltage with ignition on and got a result of 0.38v I tested this at half open throttle and got a result of:2.23v and at wide open throttle i got a result of:3.78v
A tps sensor works by using a input voltage and a variable resistor around a shaft to send a output voltage from .5-4.5v depending on relationship between shaft and variable resistor.The ECU should usually get a voltage of 0.5v at idle from the sensor to 4.5v at wide open throttle.There are some things that can prevent the tps from sending the correct voltage like faulty earth,faulty input and also faulty tps.I was asked to draw a circuit diagram

The picture above is the circuit I had to draw.The reason there is a output needed for the ECU to properly run the engine is because the ECU needs to adjust all the sensor to what the driver is doing for example:when the driver is driving a wide open throttle the car needs more fuel therefore the injectors needs to spray more fuel.

ENGINE COOLANT TEMPERATURE SENSOR (ECT)

The ECT is usally located where the radiator pipes meet up but this differs with different maufactures.I was asked to measure the voltage at the ECT I did this by back-probing the wire then using a multymeter on DC volts and got a result of 3.5v.This reading was taken with ignition on engine not running so it is at normal temperature.After this I started the engine and let it run for a bit and got a result of 1.1v.This shows me that this is a good ECT because as the temperature increases the voltage decreases because it is a negative coefficient.The ect works with a set resistance in the ecu that make the use able to adjust sensor to the engine.The ect voltage can also affect the fuel injection because a higher output from the ect at cold tempreature gives a higher voltage to the ecu causing it to ground injectors for longer.A faulty thermister or a faulty earth will give the ecu the wrong voltage which could cause the car to run badly.I back-probed the black wire which is earth and measured voltage with multimeter and got a result of 0.1mv this result shows sensor has a good earth.A lose connection could cause a bad earth.

above is a a ect circuit diagram and at the bottom is the actual ECT

RPM SENSOR

When testing this we put the multimeter on AC volts instead of DC.We test it by back-probeing a signal wire.Started the car and recorded my result and I got a result of 90mv at idle.I increased the engine RPM to 2500 RPM and got a result of 200mv.I put the multimeter on DC volts and got a result of 1.2v at idle and after increasing the RPM to 2500 again I got a result of 16mv.I was then asked to set me meter to read Hz and at idle I got a result of 5KHz and at 2500RPM my result was 7.5KHz.This results shows me that using AC voltage is the best way to see if the sensor is working properly and is also acurate reading.The 4a-fe engine I was using had a hall effect type rpm sensor.This type of sensor works with a magnet and a plate plate pases through the magnet then it grounds and sends a voltage out the sensor wire.It is good to use diferent functions of the meter to get acurate results it gives us an idea of what the patern would look like because we know the size and power amount of it.

I got a circuit diagram of this sensor of electro-circuit.com

The picture at the botom is a hall effect RPM sensor

The arrow poimts to the magnet and can also see it has 3 wires going to it and in the middel we can see the 4 poles.

MAP OR MAF SENSORS

We had a choice between MAP or MAF sensor I used the MAP sensor because the engine I did my work on used a MAP.
I backprobed the sensor to get a voltage reading.I did this and with ignition on car not running I got a result of 1.8v.I started the engine and let idle for a bit and got a result of 0.5v.After this a gave it a quick acceleration and got a result of 1.8v.The map sensor works with presure and measures it and sends it to ECU with the signal wire and the ECU adjust the engine to that result by using other sensors.the readings i got was correct because it went up when short acceleration because there is more preasure.bad conection or pipe not on could give ecu bad reading

INTAKE AIR TEMPERATURE SENSOR

I bak-probedthe sensor and turn the ignition on and measured voltage and got a result of 3.3v.This reading is 0.2v less than that of the ect.This show that the iat is hotter than the ect.The IAT works by measuring the temp goin through the intake and sending it to the ecu.The IAT voltage effects the ecu for fuel injection in the same way as the ect if it is wrong the injotor time would be wrong.The sensor signal sends out a higher signal if the tem rises.A bad connection or bad earth can cause the incorect signal for the ECU

CAMSHAFT POSITION SENSOR

With the following sensor i did not go to deep into it just got the 4 differint readings with a multimeter.

DCvolts:19.5mv
ACvolts 1.2v
hertz:0.09kz
%duty cycly:14.1%
These results showed me that the best way to measure this was with duty cycle