1.0 Battery Voltage to Injectors (Warning: Petrol Vehicles Only. Some diesels will have dangerously high voltage to fuel injectors.)
1.1 Locate a fuel injector
1.2 Back-probe the wire to the fuel injector by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside.
Don’t puncture or damage the wiring. Hook up your multimeter red lead to read dc volts. Make sure the meter black lead is grounded.
1.3 Make sure students and meter leads are clear of moving parts, and start the engine.
1.4 Record the voltage to the fuel injector: 14.01 V
Discuss why would we bother checking the voltage supply to the fuel injectors?
So we know that are firing like they are working properley and there is no high resistance in the injector circuit.we have to make sure they are working correctly and if we dont have the supply voltage we could have fault with the injectors but if we have lower voltage in the injectors than the battery we would have resistance in the circuit we will also be getting poor operation lack of fuel injections or could even have non .
Draw a full circuit diagram for the fuel injectors, including battery ,ignition switch, main relay and how the injectors are switched:
Reference Voltage at TPS sensor
The purpose of the reference voltage to the throttle position sensor is the voltage going to the TPS is the TPS is not getting voltage from the ECU then the TPS wont deliver the right signal and a lot things can create problems for the reference not to get the right reference voltage for example if there is dirt building up on potiontelmeter which can cause high resistance and you might come across a loose connection.if the reference volatge is not right because there is high resistance in supplied wires they could not be plugged in properly , corroded also broken wires and this can cause the ECU wrong signal for example if the throttle is wide open but only have is received . And this can create fuel economy poor engine performance. Closed throttle meaning there is high resistance and out voltage will be low when its fully open you will get low resistance but high output voltage so thats how ECU knows which state is a throttle and it can also determine how fuel to add.
Ground at TPS sensor
Back-probe the sensor ground or earth wire by inserting a pin down therubber insulation far enough to connect with the metal wire terminal on theinside. Don’t puncture or damage the wiring. Hook up your multimeter red lead to read dc volts. Set the meter range or scale to 4V or less. Make
sure the meter black lead is grounded on engine block or battery.
Record the voltage on the meter 0.00V (A good ground will usually read less than 0.05V. Some manufacturers say 0.10V.)
The reason why it is important to measure the ground voltage is because alot of things can happen if its higher. This voltage reading shows us the resistance in the ground wire of the TPS if high the ECU gets faulty reading because voltage is lost and its trying to push current through the wires.
And if the ECU dont have good earth or ground anything can cause that problem for example there could be bad wire connection or corrosion on battery terminals.
Throttle Position Sensor return/output:
With the engine NOT running, back-probe a likely wire for the TPS input by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside. Do not damage the wiring. Set up
the voltmeter to read DC Volts. Attach meter red lead to the pin; attach black lead to a good ground.
Record the reading from the meter. 0.573 If you do not get a reading on the meter, you may have to check for a good connection, or try different wires until you get a good reading to record above.
Open the throttle to about the half open position, (make sure engine isnot running) and record the reading on the meter 2.00v Close the throttle.
Open the throttle to the full open position, (make sure engine is not running), and record the reading on the meter: 2.910v Close the throttle.
Slowly open the throttle from the closed position to the full open position,and watch that the meter readings slowly increase with no sudden jumps or gaps in the signal. OK
The way TPS work as the throttle valve opens it idecates more air coming in .A viper arm is connected mechanically to the throttle valve . As the valve more so does the viper arm on a resister the different resistant pick up tell you the TP. TPS is sends two different types of voltages to the ECU so when the throttle is closed
there will be low voltage as it opens the voltage goes higher for example when the TPS is open the sensor voltage will increase but when its closed the voltage will decrease. And heaps of things could stop the TPS to send the correct voltage to the ECU for example if there dirt on potentiometer the ECU could be getting the wrong readings or might not even pick it up and there could also be loose connection you never know a lot of things can cause problems.
4.91 Draw a full circuit diagram for the TPS on this vehicle:
ECT (Engine Coolant Temperature) Sensor
With the engine Not running, back-probe a likely wire for the ECT supply by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside. Do Not damage the wiring. Set up
the voltmeter to read DC Volts. Attach meter red lead to the pin; attach black lead to a good ground.
Record the reading from the meter: 2.522 v
Is the engine cold, between cold and normal temperature (warming up), or
at normal operating temperature? Yes warming up
Does the voltage reading above seem right for the temperature of the
engine? (yes or no) Yes
Make sure all students and meter leads are clear of the engine. Start the
engine. Let the engine warm up for about two more minutes, and record
the voltage of the ECT sensor now: 2.071v
A warmer engine should usually show a lower voltage. Is the reading
above lower than the first reading? (yes or no) yes
how an ECT sensor works.?
The ECT sensor responds to the change in engine temperature by measuring engine coolant temperature the ECm knows the average temperature of the engine . The ECT sensor is important for many other things like transmission shifting fuel injection ignition timing and a lot of other things. So when engine temperature becomes warm then the voltage drops so as the temperature rises the resistance goes down this is referring to the Ohms law V=IR .So what this tell us that when the engine is cold more fuel will be used but if its hot then you will be using less fuel.Like i mention before the ECT responds to the engine temperature by measuring the engine coolant temp it will run in that condition for example when you start your car in the morning it will be cold and if you dont let it warm up then you will be using more fuel but if you let it warm for a bout 2 to 3 mins then you will be using alot less fuel then cold.And all this happens by the signal to the computer that indicates
if less or more fuel is needed .A lot of things can create incorrect voltage to the ECU for example there could be bad battery connection on battery terminals if it send incorrect voltage the ECU wont know the correct temperature of the engine running and this can cause problems with the fuel ratio it will the effect the lean or rich mixture .
Ground Coolant Temperature Sensor
Record the voltage on the meter: 0.00v (A good ground will usually read less than 0.05V. Some manufacturers say 0.10V.)
This voltage reading shows us the resistance in the ground wire of the CTS if high the ECU gets faulty reading because voltage is lost and its trying to push current through the wires.
And if the ECU dont have good earth or ground anything can cause that problem for example there could be bad wire connection or corrosion on battery terminals.
Draw the circuit diagram for the ECT sensor for this vehicle. Include some detail inside the ECU.
RPM Sensor or Crank Position Sensor (CKP):
With the engine Not Running, back-probe a RPM signal wire by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside. Do Not damage the wiring.
Set up the voltmeter to read AC volts. Attach meter red lead to the pin; attach black lead to a good ground. Make sure the meter leads are clear of moving parts for when you start the engine.
Record the reading from the meter: 3.40V If you do not get a reading on the meter, you may have to check for a good connection, or try another wire. Turn off the engine when you switch to another wire, then restart
the engine and check for a reading. Try different wires, or get help from your Lecturer until you get a good reading to record above.
Increase engine RPM to about 2500 rpm. Record the reading from the meter: 6.6V
Return the engine to idle speed. Switch the voltmeter to read DC volts.
Record the reading from the meter: 0.7V
Increase engine RPM to about 2500 rpm. Record the reading from the meter: 1.16 V Return the engine to idle speed.
Switch the voltmeter to read Hz. Record the reading from the meter: 530 Hz (Some MAF sensors output is a Hz signal, some is an analogue voltage signal)
Increase engine RPM to about 2500 rpm. Record the reading from the meter: 1265 Hz Return the engine to idle speed, and shut off the engine.
Which setting best showed if the RPM sensor was working AC volts , DC volts ............ … or Hz : Hz
I am not really sure how the senor really works so i did some research to try and find out so i hope i am right
The function of crank sensor is to measure the speed of the when we were doing the test we had to get a reading when it was running normal and also we had to to rev it up to 2500rpm so the reading we got shows us that when the engine is faster we get higher readings when the ECU knows this information then it will atuomaticlly know how the engine is running and also this info is used by the ECU to know when to turn on the fuel injectors. a lot of things can cause problems so the ECU doesnt get the correct reading for example if the they not firing at the correct time then the ECU will not receive the correct the engine will crank but it wont start .
MAP or MAF Sensor:
when we were testing the MAP sensor we take voltages at two different points one was with the ignition on but the engine not running so the reading i got for that was 1.832V and then we had to turn on the car let it idle and the reading i got for that was 0.45V we also had to step on the throttle to get quick but short acceleration and the reading i got for that was 1.2V . This tells us that as the pressure builds up in the intake manifold the silicon ship in the MAP sensor flex crossing changes in resistance so this alters the voltage reading to the ECU and the reading we got was correct because when the engine is off we have max voltage at the MAP but when turned on and on idle it goes down slowly and when we do sudden acceleration crossed high in vacuum for small time.A lot of things go wrong for the ECU not to receive the correct voltage for example if the reference chamber leaking on the vacuum that can cause wrong reading for the ECU.
If the signal is incorrect this can cause then the ECU will be running at that signal this could be lean or rich but this can also cause back fire in acceleration the engine will be running rough .
Draw the circuit diagram for the MAP sensor on this engine in the box below:
IAT (Intake Air Temperature), ACT (Air Charge Temperature), or MAT (Manifold Air Temperature Sensor
For i IAT sensor we had to take measurements at different stages the first one was we had to turn on the ignition but dont start the engine the reading i got for that was 3.422V and then we had to compare it to the ECT senor like the reading we got for IAT senor is less the than what we had for ECT sensor we also had compare the temperature wise and what we had for IAT senor is colder then ECT sensor . IAT sensor has a
varible resistance which cools it when air hits it this causes the resistance to change therefore changing in voltage .it works prety much the same as ECT sensor so when its cold then you will need more oxygen because there is more fuel spraying . for example if the engine is cold then we will be using more because
Co2 dence more air but if its hot then we will be using less fuel because Co2 less dence air.If it gets out wrong input signal the we could have air ratio also engine will be running rough. IAT sensor changes to different temperature condition for example if we have cold air temperature then IAT signal will get high voltage but if the air temperature is hot then it will low voltage it will send the voltage accordingley to the temperature of the air. A lot of things can create incorrect IAT signal for the ECU for example if there is dirt on the resistor or bad connection also bad earth could can create incorrect signal.
Draw the wiring diagram for the IAT sensor for this vehicle. Include some detail inside the ECU
