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: 13.75v
1.5 Discuss why would we bother checking the voltage supply to the fuel injectors?
We have to check the voltage getting there to work properly. Without voltage or wrong voltage in the fuel injectors will affect its function.
1.6 If we find lower voltage at the injectors than at the battery, what can that mean? And how would injector operation be affected?
Lower voltage means there is a resistance which is causing the voltage to drop and less power of the engine.
1.7 Draw a wiring diagram that shows how voltage gets to the fuel injectors and what wires are involved:
2.0 Reference Voltage at TPS sensor
2.4 Record the reading from the meter: 5.02v
This is good reading.
2.5 What is the purpose of the reference voltage to the Throttle position sensor?
The purpose of the reference voltage is to keep the sensor on or alive and tells the ECU it is alive so the computer can calculate the reading and determine the fuel required from the throttle valve angle.
2.6 What could cause problems so that there is not the correct reference voltage at the throttle position sensor?
Yes there will be a problem if there is no reference voltage and the TPS will not be on and will not give correct signal.The engine will not run fine. ie. Could cause hesitation
3.0 Ground at TPS or ECT Sensor
3.3 Record the voltage on the meter: 0.082v. (A good ground will usually read less than 0.05v. Some manufacturers say 0.10v)s voltage tell you about the computer earth or ground?
3.3 What does this voltage tell you about the computer earth or ground? Why is it important measure it?
It tells us that circuit is completed and all the supply voltage is used up, if it reads high so there is problem or open circuit.
3.4 Discuss what could go wrong so that the ECU earth or ground is not good:
It will not give any signal to computer as there could be bad connection to the earth which does not complete the circuit poor connection.
Throttle Position Sensor return/output:
4.2 Record the reading from the meter: 0.62v. 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: 3.2v
Close the throttle.
4.4 Open the throttle to the full open position, (make sure the engine is not running), and record the reading on the meter:
Close the throttle.
4.5 Slowly open the throttle from the closed position to the full open position,l and watch that the meter readings slowly increase with no sudden jumps or gaps in the signal. Ok
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 Volts readings. Record the colour of this wire: green. NB: 11.95 when the throttle is fully open and zero when it is closed.
4.7 Describe how a TPS sensor works?
This sensor works on a variable resistor as the throttle opens the sensor sends stronger signal and the ECU guide for more fuel to be delivered.
4.8 Discuss what type of sensor voltages should go to the ECu as the throttle is opened and closed:
When the TPS opens it sends a higher voltage signals but when it closes it sends lower voltage
Open - high voltage
Close - lower voltage
4.9 Describe problems which could occure to prevent the TPS from sending the correct voltage to the ECU:
If does not send the right signal the computer will not pick up how much air has enlared the manifold unit so the system could be lean or Rich so this could be caused by poor connection or TPS could be jammed due to dirt.
4.91 Draw a full circuit diagram for the TPS on this vehicle:
5.0 Throttle Position Switches:
Idle wire: Colour: Blue
Colts at Idle: 2.9mv
Volts at part throttle or open throttle: 11.95v
Wide Open Throttle wire: Colour:
Volts at idle or part throttle:
Volts at open throttle:
5.3 By watching the voltages above, figure out the circuit diagram for this TPS, and draw it in the box below.
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 ECU needs the correct signal for the amount of air entered so the ECU can guide for the right amount of fuel needed TPS less open less air and ECU will give signal for less fuel TPS more opened more air and ECU will guide for more fuel to be sprayed.
6.0 Locate the ECT sensor on your vehicle.
6.3 Record the reading from the meter: 2.36v.
6.4 Is the engine cold, between cold and normal temperature (warm up),or at normal operating temperature? Cold
6.5 Does the voltage reading above seem right for the temperature of the engine? Yes
6.6 Start the engine. let the engine warm up for about two more minutes, and record the voltage of the ECT sensor now: 1.4v
6.7 A warmer engine should usually show a lower voltage. Is the reading above lower than the first reading? Yes
6.8 Describe how an ECT sensor works?
When the engine was warm the ECT sensor whowing 1.55v when its got more hot the ECT sensor dropping the voltage to 0.95v so the sensor works good.
6.9 Describe how the ECT sensor voltage affects the fuel injection output from the ECU?
As the temperature of the engine increase the voltage and resistance drops the signal to the computer indicates that there is less fuel demand and less fuel will be consumed.
6.10 Describe what could go wrong to create an incorrect voltage for the ECU:
If they gives wrong signal to the computer so the computer will give wrong guidance for fuel according to the signal there for the engine will run rich or lean.
7.0 Ground Coolant Temperature Sensor
7.4 Record the voltage on the meter: 0.03v (A good ground will usually read less than 0.05v. Some manufacturers says 0.10v)
7.6 Discuss what could go wrong so that the ECU earth or ground is not good:
If it gives wrong signal to the computer so the computer will give wrong guidance for fuel according to the signal there for the engine will run rich or lean.
6.11 Draw the circuit diagram for the ECT sensor for this vehicle. Include some detail inside the ECU.
4.0 RPM Sensor or Crank Position Sensor (CKP):
4.5 Record the reading form the meter: 3.90v. If you do not get a reading on the meter, you may have to check for a good connection, or try another wire.
4.6 Increase engine RPM to about 2500 rpm. Record the reading from the meter: 0.713v.
4.7 Return the engine to idle speed. Switch the voltmeter to read DC volts. Record the reading from the meter: 0.70v
4.8 Increase engine RPM to about 2500 rpm. Record the reading from the meter: 1.30v. Return the engine to idle speed.
4.9 Switch the voltmeter to read to Hz. Record the reading from the meter: 650.5 Hz. (Some MAF sensors output is a Hz signal, some is an analogue voltage signal)
4.10 Increase engine RPM to about 2500 rpm. Record the reading from meter: 1.60 KHz. Return the engine to idle speed, and shut off the engine.
4.11 Which setting best showed if the RPM sensor was working AC volts DC volts 3.90AC.
4.15 Draw the wiring diagram for the IAT sensor for this vehicle. Include some detail inside the ECU.
10.0 Camshaft Position Sensor (CMP)
10.3 Record your meter readings below in the different setting, and discuss which settings show the CMP is good.
DC Volts: 1.1 mv
AC Volts: 0.2v
HZ (hertz): 0.07KHz
% Duty Cycle: 2.89
Frequency hertz and Duty Cycle %
Duty cycle as the best to understand the CMP sensor.
10.4 Draw the circuit diagram for the Cam Position Sensor on this vehicle:
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