Make:Toyota ...Modle: 1ZZ ...Year:1993.
Notice: Be careful of moving parts on the engine when you do these tests. If vehicle is diesel or hybrid that contains high voltage, it can kill you.
Discuss why would we bother checking the voltage supply to the fuel injectors?
- This could effect the inlet vale as if less voltage is supplyed the value could open sluggish or not open at all resulting in failier to put in the rite amount of fuel in to the chamber
- if we were to sense a folt the injection field then the first test would we would do is chek the voltage supply to the injector.
If we find lower voltage at the injectors than at the battery, what can that
mean? And how would injector operation be affected?
- The battery could be not fully charged.
- It is usfull to do a voltage drop test first. (Chek the battery)
- Less voltage at the inlet means the inlet valve could be not full open, struggling to open or not opening at all.
- the injectors could put out less fuel witch means the engine will be running leaner.
- this means the injection operation is bin effected (eg. voltage spike, the ECU is sending a wrong signal to the injector)
Draw a full circuit diagram for the fuel injectors, including battery ,ignition
switch, main relay and how the injectors are switched:
2.0 Reference Voltage at TPS sensor
2.4 Record the reading from the meter: Is this an acceptable or unacceptable reading? If you do not get the
correct reading on the meter, you may have to check for a good connection, or try another wire until you get a good reading to record above.
2.5 What is the purpose of the reference voltage to the throttle position sensor?
- The voltage increases when the throttle is open, therefor we know when the butterfly is open in the throttle body. to chek howmuch voltage is entering the throttlebody when the RPM goes high.
- This TPS sensor seems to be working fine.
- The purpose of measuring the reference voltage is to see if the voltage back to the sensor from the ECU in the input wire is correct , if there is a wrong reading at the referenc voltage we know that the ECU is not calculating the voltage rite.
What could cause problems so that there is not the correct reference
voltage at the throttle position sensor?
- ECU connection coud be short cuirciting or the sensor could be giving wrong readings to the ECU making the car run rough and give a wrong voltage at the throttle possition sensor.
- Also the sensor could be worn out the it cannot sense the air intake propperly.
- loose grounding at the sensor.
Ground at TPS sensor
3.2 Make sure students and meter leads are clear of moving parts, and start the engine.
3.3 Record the voltage on the meter: 0.002 mv (A good ground will usually read less than 0.05V. Some manufacturers say 0.10V.)
3.3 What does this voltage tell you about the ECU earth or ground? Why is it
important to measure it?
- To chek if the grounding is properly connected.
- I got a reading of 0.002Mv if the reading is lower than 0.05v then the sensor is in good conditon.therefore we know that acordig to the sensor specifications the grounding is in good conditon.
- ECU earth grounding is good when cheked
3.4 Discuss what could go wrong so that the ECU earth or ground is not good:
- Crrotion at the grounding point of the sensor.
- The electrics on the car mite act diffrent the Engine light mite be on ..(the lights on the dash mite do what thy want to)
- if the car has a digital Km radar this could bunddle up the numbers.
- Also this folt an effect other things like the runing conditions of the engine ( for example the readings the sensors give to the ECU on the return signal wire mite be calculated wrong by the ECU allowing the engine to run un-economical and struggling.
Throttle Position Sensor return/output:
4.1 Make sure all students are clear of the engine. Turn the ignition “on”, but don’t start the engine.
4.2 Record the reading from the meter: 0.577mV . 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.
4.3 Open the throttle to about the half open position, (make sure engine is not running) and record the reading on the meter: Close the throttle. 2.426V
4.4 Open the throttle to the full open position, (make sure engine is not running), and record the reading on the meter: Close the throttle....3.89V
4.5 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. ....PASS
4.6 If your vehicle has four wires going to the TPS sensor, continue with these
next steps to read the idle switch circuit. Locate the idle switch wire. It will
usually read about 0V when the throttle is closed, and 12 – 14V when the
throttle is opened. Back probe the different wires until you locate the wire
that gives these DC Volt readings. Record the colour of this wire: ...Yellow
Describe how a TPS sensor works
- It looks at how hard you are stepping on the accelerate. It senses how hard the engine is working (looks at the throttle positioning),
- This then sends a signal to the ECU from the input wire witch tells the injectors how much fuel is needed, this is determined by the Throttle position sensor and the RPM the car is running at.
- This sensor is a variable resistor therefore the resistent on the sensor changes according to the throttle positioning..
- this sensor is rite near the throttle butterfly therefore the signal measured my the sensor is measuerd directly from the throttle shaft and sendt to the ECU.(there is no voltage lost)
- When i tested the sensor input at Idle the voltage reading would stay around 0volts, as the acceleration goes up the voltage goes up to 5Volts while the resistent goes down
Discuss what type of sensor voltages should go to the ECU as the throttle is opened and closed:
- At Idle the throttle is slightly open letting only a fraction of air in to the engine 0volt signal go to the ECU, at higest it should be lower than 1V.
- When the throttle is fully open there is a voltage reading is higher, however the input wire sends a reading of lower than 5 Volta go in to the ECU
Describe problems which could occur to prevent the TPS from sending the
correct voltage to the ECU:
- The sensor could be old or worn out.
- Loose wiring or rusty connection at ground on the sensor could effect the Voltage reading on the output wire back to the ECU.
- If the throttle shaft is loose or the resister in the sensor is not resisting according to the air flowing in to the engine.
- If the throttle positon sensor is wired away from the throttle body the voltage reading back to the ECU could be lower than usual.(5volt at full throttle, 0volts at idle)
Draw a full circuit diagram for the TPS on this vehicle:
Throttle Position Switches:
5.2 Back probe the wires to the TPS with the ignition on but engine not running. Open and close the throttle with the meter connected, and locate which wire has the voltage which changes at idle, and which wire has the
voltage which changes near wide open throttle. Record wire colours and voltages below.
Idle wire: Colour:.............................. Green
Volts at Idle .....................................0.554V
Volts at part throttle or open throttle: 3.8800V
Wide Open Throttle wire: ................Colour:Blue
Volts at idle or part throttle: ..............1.330V
Volts at open throttle: .......................5.795V
5.4 Why is this output needed for the ECU to properly run the engine? How do these outputs change how the engine runs in the different conditions of idle, part throttle cruise, and wide open throttle power?.
- The output voltage determins how much the Throttle shaft is open wich lets the air in to the engine.
- This signal is sent to the ECU threw the output wire, according to the voltage signal the ECU decides how much fuel mixcher is put in to the cylinders, if the voltage signal on the output wire back to the engine is incorrect this could result in the injectors putting more fuel making the engine run richer, (less economical), This is because the ECU mite get a wrong reading from the sensor and think that the engine needs more fuel to run smoother, and efficiently.
- Also morning starts would be dificult because of the wrong reading.
- the TPS sensor has to have a proper reading according to the angle of the shaft otherwise the engine mite performe in poor conditions.
ECT (Engine Coolant Temperature) Sensor
6.3 Record the reading from the meter: 1.748V.. . 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.
6.4 Is the engine cold, between cold and normal temperature (warming up), or at normal operating temperature? Cold
6.5 Does the voltage reading above seem right for the temperature of the
engine? (yes or no) YES
6.6 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:1.07V
6.7 A warmer engine should usually show a lower voltage. Is the reading
above lower than the first reading? (yes or no)Yes
6.8 Describe how an ECT sensor works.
- The engine coolant temperature sensor resistance changes acording to engine coolant temperature. The sensor resistance decreases as the surrounding temperature increases letting a bigger reference voltage signal to the ECU which indicates engine coolant temperature on the dashboard and accordingly supply the rite amount of fuel injection...
Describe how the ECT sensor voltage affects the fuel injection output from the ECU.
- IF the engine coolant temperature is Cold the ECU tells the injecters to put more fuel in (run richer),were is if the engine is worm it senses that the engine temperature is worm, therefore the injecters would put out normal amount of fuel threw the injectors.
- As saying that if the enine is cold and it is running richer, this only happens till the engine goes worm . ones it worm up the ECU adjusts the fuel injection to a smoother more economical flow.
Describe what could go wrong to create an incorrect voltage for the ECU
- Bad connection at the input or ground at the sensor or even to the Ecu.(usually corrotion, loose plug)
- worn out ECT sensor.
- Dirty sensor, (would struggle to read a voltage)
7.0 Ground Coolant Temperature Sensor
- Record the voltage on the meter: .0.2 mV. (A good ground will usually read less than 0.05V. Some manufacturers say 0.10V.)
7.5 What does this voltage tell you about the ECU earth or ground? Why is it important to measure it?
- That it is in a good ground.
- Good ground is important for sensor becouse it mite couse the engine to run struggling, because the Voltage sent to the ECU could go wrong..
- It is important to measure this voltage so we know the sensor grounding is not a issue.
7.4 Discuss what could go wrong so that the ECU earth or ground is not good:
- If the sensor ground is not connected properly.(mostly rusted because it is near moisture.
- Old / dirty sensor.
- if the coolant is not touching the sensor
- Reference below
4.0 RPM Sensor or Crank Position Sensor (CKP):
- the voltage reading from the meter: 0.3mv. after increasing the engine RPM to about 2500 rpm. Record the reading from the meter: 1.8mv
- When the voltmeter used to read DC volts. the reading from the meter was: 0.7mv
- after Increasing the engine RPM to about 2500 rpm. I recoded the reading from the meter:0.7mv. . Return the engine to idle speed.
- Then we Switched the voltmeter to read Hz. Then Recorded the reading from the meter: 0.055Khz. (Some MAF sensors output is a Hz signal, some is ananalogue voltage signal)
- I increased the engine RPM to about 2500 rpm. Record the reading from the meter was:0.1324Hz
- according to my knoledge i think the best showed if the RPM sensor was working AC volts is measured by ,Hz
4.12 Describe how this type of RPM or Crank sensor work.
- This sensor has a permanent magnet ,a yoke and a oil, this sensor is bolted near a toothed gear, as each teeth moves by the sensor, an AC voltage pulse signal is created and sent to the coil, each tooth makes a pulse, faster the tooth spins more the signals are, the ECU determines the speed the component is revolving compared with the number of pulses sent.
- Usually the number of pulses produced in one second is a signal frequeny
- this sensor measures how fast the cranksharf is spinning, this information is changed in to voltage and sent to the ECU ,witch then manages the ignition timing according to the spinning of the crank shaft.
accurately measure the sensor output when you don’t have anoscilloscope available?
- If the is a Hz function that would give a propper reading.
- % and Dc voltage test could give similer readings.
What can go wrong so the ECU did not receive the correct signal from the
RPM or Crank sensor:
- The ECT sensor could have a bad grounding,
- BAd ECT sensor.
- Worn out wires at the connection points.
5. MAP or MAF Sensor:
- With the ignition “on”, but not start the engine the voltage reading we got on the meter is:0V ,
- after starting the engine Letting it settle to idle. i got a voltage reading of 1.49v.. .
- Then i Stepped on the throttle to get quick, but short acceleration of the engine. not reving the engine up too high I Record the increased reading on the meter:3.02V
5.10 Describe how the MAP sensor works to tell the engine how much air
comes into the engine?
- This sensor measures the engine load then sends a signal to the ECU .
- when i turn on the ignition without starting the engine i got 0V.
- when i started the engine and recorded the voltage at idol ,it was abit higher.
- i got a reading of1.49V,
- When I increased the RPm to 2500 RPM i got a voltage of3.02V,
- These readings show that the hiyer the negative force is (RPM), the lower the recistenc becomes and lower the negative pressure is higher the resistant becomes.
- if there is a bad grounding or bad wiring some were some were this could give a wrong reading.
- if there is a leek in the hoses it could give us a wrong reading, in saying that the engine memerises this and puts extra fuel in to make it run smoother . it is best to backprobe check the voltage.
This video really helped me understand how the MAP sensor testing.
9.0 IAT (Intake Air Temperature), ACT (Air Charge Temperature), or MAT
(Manifold Air Temperature Sensor
9.1 Locate the IAT type sensor on your vehicle.
9.2 With the engine Not running, back-probe a likely wire for the IAT 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.
9.3 Make sure all students and meter leads are clear of the moving parts of the engine. Turn the ignition “on”, but don’t start the engine.
9.4 Record the reading from the meter: 2.25v.. 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.
9.5 Is the reading more or less than the reading you had for the ECT?
less.
Does this show the IAT sensor is colder or hotter than the ECT sensor?
hotter
9.6 Describe how the IAT sensor works.
- .This sensor helps the ECU to calculate the air density.
- Chang in temperature changes the resistant in the sensor.
- basikly higher the temperater is lesser the density becomes.
- as the air gets less dense the computor is designed to pt less fuel.
- If it is not changed the engine will be running rich.
Describe how the IAT reading affects the ECU outputs for fuel injection. Include how an incorrect input could affect the fuel injection and engine
- According to the air density the computer adjust the fuel flow .
- if the density is low then there is high fuel presser.(richer)
- If the density is low then there is low fuel presser(leaner)
- if there is a higer input voltage at the sensorthis could result in many insidents like loss of power and hiyer usage of fuel.
Describe what could go wrong to create an incorrect IAT signal for the ECU:
- A bad sensor or bad grouning.
- leak in the airflow piping or even a blockage.
10.0 Camshaft Position Sensor (CMP)
10.1 Locate the Camshaft Position Sensor on a vehicle. This may be near the camshaft or it may be in the distributor.
10.2 Locate the wire that carries the signal to the ECU. Back probe the wire to measure the signal. Experiment with different settings on your multimeter to see which best indicates that the CMP signal is good. (DC volts, AC volts, HZ, or % Duty Cycle)
10.3 Record your meter readings below in the different settings, and discuss
which settings show the CMP is good.
DC Volts:........ 0.715V
AC Volts: .......1.0mV.
HZ (hertz):.......0.000Hz
% Duty Cycle:. 0.1trig=%
My opinion the duty cycle calculates the best camshaft positioning ..
