The picture above is a picture of the circuit I drew with all the components named.
The next sensor I did was tps (throttle position sensor).The tps has a 5v reference in this case it was the yellow wire.The reason for a 5v reference is because it is the power to the sensor this is to provide a good signal to the tps.Sometimes the reference voltage could be wrong.This could be caused by a high resistance in the feed because it is a straight feed.The next test I did was testing the ground at tps sensor.I used a pin to back-probe the sensors earth.I used a multimeter I put the red terminal on the pin and the black terminal on the engine to ground it I put my multimeter on dc volts and got a result of 0.002v.This result shows me that there is a good earth.This is important because if there is a bad earth the car wont run properly.A broken earth wire can cause the ECU to have a bad earth.I located a tps input and back-probed the wire measured voltage with a multimeter with the ignition on and got a result of 0.384v.I opened the throttle half way and got a reading of 2.23v then i opened the throttle all the way and got a reading of 3.789v.I did a test by slowly opening the throttle fully from closed and watched the reading increase slowly this means it is good result.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.
The next sensor I tested was the engine coolant temperature sensor.
I found the ect on this engine then I back-probed the supply wire to the ect.I turned the ignition on and used my multimeter to measure the voltage at this point and I got a result of 3.58v.The engine is at normal temprutare at this point.I started the engine and measured voltage again and I got a result of 1.1v.This result shows the sensor is good because the voltage decrease whhen the engine tempreture increases.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.
The next sensor I did was the rpm sensor.
To test this sensor I back-probed a rpm signal wire with a pin and put my multimeter on ac volts.I strarted the engine and measured the voltage and got a reading of 90mv.I increased the rpm to about 2500 and got a reading of 197mv.I switch the multimeter to dc volts and at idle I got a reading of 1.2v.I then again increased the rpm to 2500 and got a reading of 16mv.I then switched the meter to Hz and got a reading of 5kHz after increasing rpm again I got a reading of 7.5kHz.These result shows that Ac voltage was the best way to see if the rpm sensor is working.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.
The next sensor i did was map or maf sensor.
I backbrobed the map sensor and measured the voltage with the ignition on and got a result of 1.8v.I started the engine and let it idle measured it and got a reading of 0.48v.Then i gave it a quick short accelaration 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
The next sensor I tested was the IAT(intake air temp)
I had to back-probe the 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
Next sensor was camshaft position sensor
I had to measure the cmp in 4different settings to find the best one.
DCvolts:19.5mv
ACvolts 1.2v
hertz:0.09kz
%duty cycly:14.1%
duty cycle best way to measure this.
At level for a expect your circuit diagrams to be drawn to a curtain standard
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