Input Sensors and Actuators On-Vehicle

TOYOTA 1ZZ
1. Fuel Injectors
Back probe the wire to the fuel injector by inserting a pin and red lead of multimeter connects the pin. Another black lead touches the earth. Then, the engine starts and record the voltage to each fuel injector.
#1 Injector 14.18v, #2 Injector 14.18v, #3 Injector 14.17v, #4 Injector 14.18v
The injector operation voltage is same as battery voltage at near 12v. From supply voltage, the injectors properly work with creating magnetic field and movement of piddle. Therefore, the supply voltage of injectors should be checked for correct operations. It is a important factor for fuel injection. 
If I find lower voltage at the injectors than at the battery, the weak magnetic field will produced the around coil and the injectors will not fully open with less fuel injection. So, the engine will not run properly, such as lower engine power and unstable idle. The engine will also get abnormal conditions.
Injector circuit diagram

2. TPS sensor

Turn the ignition on. Back-probe the three wires to the TPS sensor by insertion a pin. Then, a black lead of a multimeter connects the ground and a red lead touches the three wires in order. When the throttle is closed and fully opened, record the reading from the multimeter.

The reference voltage of the ECU supplies main voltage for sensor's operation at near 5v.

 Incorrect reference voltage cause problems that the sensor does not get output signal voltage and the ECU will not connect with abnormal engine operation with less power and high emission.  

Back-probe the sensor ground(a brown wire) wire by inserting a pin. Then, a black lead of a multimeter connects the engine ground and a red lead touches the inserted pin.  read the voltage at 0.03v. This sensor has good ground connection which should be less than 0.05v.

There is not a big voltage drop between sensor's ground wire and the engine earth which means that the sensor will operate correctly and the good connection makes the correct results for TPS sensor's operation. A bad ground connection causes wrong TPS's work and the ECU controls wrong fuel injection, such as the corrosion of connectors, contaminated connectors and wires and loose connection.

Throttle Position Sensor return/output

Potentiometer Type : Back-probe the sensor signal (a green wire) wire by inserting a pin. The red lead of a multimeter connects this inserted pin and another black lead of the multimeter touches the earth. When the throttle is closed, the output voltage is at 0.649v. However,  when the throttle is fully opened(WOT), the sensor output voltage is at 3.98v.

Yellow wire : Supply voltage 5v (reference voltage)

Green wire : Output voltage (signal voltage)

Brown wire : Earth (ground)

The sensors give the ECU information about the throttle positions with its voltage values which shows idling status and wide open throttle status. As a result, the ECU controls idle stability, proper acceleration and deceleration according to the acceleration pedal positions. When the corrosion is created the inside of TPS sensor with its resistance, this problem prevents the TPS from sending the correct voltage to the ECU. The other problems are bad and loose wire connections and any unstable connections.

3. RPM Sensor or Crank Position Sensor(CKP)

Set up the multimeter to read AC volts. A red lead of a multimeter attaches sensor signal and a black lead of the multimeter touches a good ground. When the engine starts, the multimeter shows the voltage reading at idle, at 0.116v. When the engine rpm increase to 2500rpm, the voltage value also goes up at 0.204v. When the multimeter is set up DC volts, voltage values are not stable both idle and high rpm. 

 On the Hz range, reading values of the multimeter both idle and 2500rpm are similar at around 0.1Hz. Therefore, When the RPM sensor measures for its correct working, a multimeter setting best showed AC volts range.   

Crankshaft Position Sensor(NE sensor)

The ECU uses crankshaft position signal to determine engine RPM, crankshaft position and engine misfire. This signal is referred to as the NE signal. The NE signal combined with the G signal indicates the cylinder that is on compression and the ECU can determine from its programming the engine firing order.

Pick-up coil type sensor.

The distance between the rotor and pickup coil is critical. These sensors generate AC voltage, and do not need an external power supply. Another common characteristic is that they have two wires to carry the AC voltage. This sensor is mounted close to a toothed gear. As each tooth moves by the sensor, an AC voltage pulse is induced in the coil. Each tooth produces a pulse. As the gear rotates faster there more pulses are produced. The ECU determines the speed the component is revolving based on the number of pulses. The number of pulses in one second is the signal frequency. 

I can measure the sensor output signal from using a multimeter which set up AC volt range. When the engine is running, I can see the output voltage from the multimeter.
When the loose connections, wire corrosion and the broken teeth of a gear are produced, the ECU can not receive the correct signal from the RPM or Crank sensor.

4. MAP Sensor 

 Set up the multimeter to read DC volts. A red lead of a multimeter attaches sensor signal and a black lead of the multimeter touches a good ground. When the ignition turns "on" but the engine does not start, the output voltage of the sensor is at 1.804v. When the engine is running at idle, the sensor output is at 0.53v. And then, when the sudden accelerations are produced, the output voltage increases to 1.211v.
MAP's data. The lower pressure(higher vacuum) of the intake manifold at idle produces low output voltage at around 0v in a MAP. On the other hand, the higher pressure(lower vacuum) in the intake manifold at WOT creates high output signal at just under 5v in the MAP.
 If the loose connections, wire corrosion and  any leaks of the intake manifold and vacuum hose are produced, the ECU would not receive the correct signal from the MAP sensor.

5. MAF Sensor

Set up the multimeter to read DC volts. A red lead of a multimeter attaches sensor signal (green wire) and a black lead of the multimeter touches a good ground. When the engine does not start and the ignition turns "on", the output voltage is at 0.6v. When the engine is running at idle, the output voltage goes up at 1.2v and when the engine got sudden accelerations, the signal voltage increased more to 2.5v.
Hot Wire Type
 The primary components of the MAF sensor are a themistor, a platinum hot wire and an electronic control circuit. The thermisto measures the temperature of the incoming air. The hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control circuit. An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by sending more current through the wire. The electronic control circuit simultaneously measures the current flow and puts out a voltage signal in proportion to current flow. 
 When the engine is running at idle, the sensor output voltage is low due to less incoming air. However, when the engine is running at high rpm and WOT, the  sensor output voltage is high because more air is going through the intake manifold for proper combustion.
 If the loose and bad connections, wire corrosion, bad ground and contaminated hot wire from the oil, dust and sludge are produced, the ECU would not receive the correct signal from the MAF sensor.

6. IAT (Intake Air Temperature)

Chart of Input and Outputs
Measure the signals with a multimeter, set to the right setting, and record in the boxes.

Coolant Temperature (THW or ECT) DC volts	Cold engine 2.29v	Warmed-up engine 1.055v
Throttle Position Sensor DC volts	Closed throttle 0.559v	Open throttle 3.91v
Crank or RPM sensor AC volts and Hertz	Idle rpm 2.56v / 354Hz	2500 rpm 5v / 1343Hz
MAP sensor DC volts	Idle vacuum 0.575v	No vacuum or key on engine off 1.829v
Air Temperature (THA or IAT) DC volts	Cold engine 3.49v	Warmed-up engine 2.26v
Throttle Position Switch (Idle and/or WOT) DC volts	Closed throttle -	Open throttle -
CAM sensor AC volts & Hertz	Idle rpm 0.728v / 33Hz	2500 rpm 2.239v / 67Hz
Fuel Injector Duty cycle %	Idle 0.2 %	Acceleration 59 %
Idle Air Control Duty cycle %	Idle  30.8 %	Cranking or 2500 31.7 %

Reference by

http://www.autoshop101.com/

http://moodle.unitec.ac.nz/file.php/1310/Theory/Lesson_2_Sensors/Lesson_2_Sensors.pdf

Off-Car Practical

1. TPS (Throttle Position Sensors)
- Theory
Throttle Position Sensors : The sensors give the ECU information about the throttle positions with its resistance and voltage values which shows idling status and wide open throttle status. The ECU controls idle stability, proper acceleration and deceleration according to the acceleration pedal positions. There are two types of TPS which are called Potentiometer type sensors and On-Off switch type sensors.

- Procedure 
Potentiometer type sensors
A voltage(5v) is supplied to the sensor by the ECU. When the throttle position angle is changed, the output signal will also change.

I have tested a TPS with four terminals. Vcc(Voltage Constant Control), E2(Ground), IDL( Idle Switch) and VTA(Voltage Throttle Angle)
A 5v and earth of the power supply are connected sensor's Vcc and E2 each. Then, the VTA terminal is touched a red lead of a multimeter and another black lead connects the ground as well. When I change the throttle angle, the output voltage are changed. When the angle is bigger, the voltage goes up. At closed throttle, the IDL touches the red lead of a multimeter with at 0v and IDL signal flows through the ground. When the throttle opens, the IDL is disconnected with an open circuit and the IDL voltage goes up form 0v to high voltage(12v).

On-Off switch type sensors 
This sensors detect throttle position with its switching operation at idle and WOT.  

When the red lead of a multimeter is connected the IDL and the black lead is touched the earth with the idling status, the resistance value is at 0.8Ω. When the red lead is made contact with the PSW with the WOT status, the resistance value is also at 0.8Ω. 

When the throttle is closed, the earth connects IDL and it has certain resistance with digital signal representing. On the other hand, when the throttle is widely opened, the earth touches PSW and it also has certain resistance. As a result, when the engine is idling, the ECU knows that the throttle is closed from the resistance value. When the acceleration pedal is fully pushed, the ECU knows that the throttle is opened from its resistance value.

- Reflection

The TPS gives the ECU the position of an acceleration pedal, then the ECU controls fuel injection and the change of engine rpm and power. If the TPS is faulty, the idle would be operated with higher rpm due to wrong resistance and output voltages and the engine will not run properly.

2. MAP (Manifold Absolute Pressure Sensors)

- Theory

Manifold Absolute Pressure sensors : These sensors measure the intake manifold pressure and it gives the ECU information about the output signal. Then, the ECU controls the fuel injection and ignition timing from the MAP's data. The lower pressure(higher vacuum) of the intake manifold at idle produces low output voltage at around 0v in a MAP. On the other hand, the higher pressure(lower vacuum) in the intake manifold at WOT creates high output signal at just under 5v in the MAP. 

- Procedure

The 5 voltage is supplied the red lead of MAP and the black lead is touched the earth. After then, the green lead of the MAP connects the multimeter's red lead for measuring output voltage. Using a mity-vac apply vacuum to the MAP. When the low vacuum is applied to the MAP sensor, the output signal is high. when the vacuum increased, the the output voltage dropped.

The sensor consists of a piezoresistive silicon chip and integrated circuit(IC). A perfect vacuum is applied to one side of the silicon chip and manifold pressure applied to the other side. When pressure in the intake manifold changes, the silicon chip flexes causing a change in its resistance. The changing resistance means a change in signal voltage.

- Reflection

 The MAP sensor gives the ECU information about the measurement of an amount of intake air(manifold pressure), then the ECU controls fuel injection and ignition timing. So, the MAP sensor are a critical factor for operating engine. If the MAP sensor is faulty, the engine would not run, get rough idle and less power at acceleration. 

 3. CTS(Coolant Temperature Sensors)
- Theory
Coolant Temperature Sensor : The sensors give the ECU information about the coolant temperature with its resistance values. Then, the ECU controls the fuel injection, ignition timing, idling speed and automatic transmission timing. When the engine is cold at starting, the sensors will produce high resistance and this signal applies to the ECU and then the ECU orders rich mixture due to the condensation of the cold engine condition. As a result, the engine rpm goes up and when the coolant temperature is gradually warmed up with lower resistance, the engine rpm will gradually decreased until fully warm-up.

The ECU can calculate the temperature from sensor's signal. Two resistors in series must drop all the voltage across them. If the first resistor(sensor) is larger more voltage is dropped accross it and the A position value will be smaller. 
 NTC Thermistor (Negative Temperature Coefficient Thermistor)
When the temperature goes up, the resistance drops. The CTS uses a this type thermistor. 
 PTC Thermistor (Positive Temperature Coefficient Thermistor)
When the temperature goes up, the resistance also increases.     

- Procedure

The engine coolant temperature sensor suspends in a container of water. The water is heated up and check the temperature with a thermometer. Simultaneously, the two termials are connected the multimeter' two leads with the ohm range. When the water was gradually heated up, the resistance values are gradually dropped. Therefore, this sensor is a NTC type thermistor.  

- Reflection

CTS is also a crucial factor for operating engine. If the sensor is faulty, the engine would not run properly which means that the CTS is related to fuel injection, ignition timing , idling speed, cooling fan and referencing data of other systems.

 4. ATS(Air Temperature Sensors)
- Theory

Air Temperature Sensor : The sensors give the ECU information about the intake air temperature with its resistance values. Then, the ECU controls the fuel injection, ignition timing, idling speed. When the intake air is hot with less oxygen, the ECU controls less fuel injection and it can make the optimum combustion condition.

The ATS also uses a NTC type thermistor. When the air temperature is high, the resistance of a sensor decreases.

- Procedure

The two terminals of a sensor are connected the leads of a multimeter with ohm's range. Then, hot air is blown by a blow gun. The resistance values are changed. When the temperature increased, the resistance of the sensor dropped.

  

- Reflection

The air temperature sensor gives the ECU information about the measurement of air temperature, then the ECU controls fuel injection and ignition timing, idling speed for proper combustion with less emission. If the sensor is faulty, the engine would not run properly.

5. Thermo Fan Switch
- Theory

When the coolant is hot, it should be cool by the fan's operation and prevent over heating. So thermo fan switch controls on-off the fan's operation according to coolant temperature. Normally, two metals are contacted with the closed circuit when the coolant temperature is cold. However, when the engine is hot with load's conditions, the thermo fan switch has an open circuit with switch on then, the fan runs and when the coolant is cool again, the switch will be off. 

- Procedure

The one terminal of a sensor is connected the red lead of a multimeter and the black lead is touched an earth of sensor's body with ohm's range. Then, the water is heated up gradually. The resistance values are at 0Ω before 94℃ When the temperature reached at 94℃, the sensor changed an open circuit with infinite resistance.

This thermo fan switch turns on at 94℃ with open circuit. The fan operates with a relay which uses a closed relay. When the voltage is supplied the relay, the relay has an open circuit.

  - Reflection
The thermo fan switch turns on a fan when the coolant temperature reaches certain temperature at around 90℃ to 98℃. If the switch is faulty, the engine would be overheated because of no fan operation or the fan would run continuously when the engine is cool which causes fan's damage.

6. Knock Sensor

- Theory
The knock sensor detects engine detonation(knock) and this sensor produces the small voltage signal when the engine knock is produced. The signal is applied to the ECU and the ECU control the ignition timing for the optimum combustion. Engine knock occurs within a specific frequency range.

- Procedure
The one terminal of a knock sensor connects a positive lead of an oscilloscope and the body of the sensor is touched the earth of the oscilloscope. When the tap is produce the end of the knock sensor, I can see the waveform on the oscilloscope screen. 

The sensor being a small piezo-electrical device that has the properties of producing a voltage when subjected to kinetic energy(knock). The tap produces certain voltage at around 10mv without supply voltage.

- Reflection

I have tested a knock sensor which produce small voltage with its frequency from tap. The ECU receives these voltage and controls the ignition timing for the proper combustion. If the knock sensor is faulty, the ECU would not controls the ignition timing when the knock produced. The engine would be damaged under knock conditions, such as a higher engine temperature, high loads, and fully opened throttle with using high power.

7. Mass Air Flow Sensor

- Theory

The mass air flow sensor directly measures the amount of intake air when the air goes through between an air cleaner and a throttle body. The sensor gives the ECU information about the output signal. Then, the ECU controls the fuel injection and ignition timing from the MAF's data. It is critical that the sensor signal uses to determine injector's operation time. 

- Procedure
Vane type air flow meters
There are seven terminals in a vane type air flow meter. The sensor is checked resistance with using a multimeter and ohm range. E2(earth) connects a black lead of the multimeter and Vs is touched a red lead of the multimeter. When the vane moves, the resistance value changes. Using 5v power, a 5v is supplied Vb(source) and the voltage is measured between Vs and earth using voltage range of the multimeter. When vane is closed, the voltage is high at near 5v. When the vane angle increases, the output voltage drops.

  

When the amount of intake air changes with vane's movement, the resistance and voltage are also changed. When the vane closes, the resistance value is the highest with the highest signal(Vs). On the other hand, when the vane fully opens, the resistance value is the lowest with the lowest voltage. Therefore, the ECU knows the amount of intake air from the signal voltage changes.

- Reflection

I have tested a vane type air flow sensor which produces voltage between 0v and 5v. When I connected the terminals for measuring resistance and voltage, I had wrong results due to faulty connections. A Vc terminal should be touched the constant 5v and a Vs should be connected multimeter's red lead. So, I could check the voltage changes according to different vane angles.

 If the MAF sensor is faulty, the ECU would not controls the fuel injection and the ignition timing due to wrong signal. As a result, the idle would be unstable or turned off the engine. The acceleration would also be abnormal with less power.

8. Speed or Position Sensors

- Theory
 Speed (Crankshaft Position sensor) or Position(Camshaft Position Sensor) sensors give the ECU information about crankshaft speed(rpm) and cylinder positions. Therefore, the ECU controls the ignition timing and correct fuel injection according to engine speed and camshaft positions. 
Magnetic Distributor
This system uses magnetic principles coupled together with an inductor winding commonly known as the pickup winding. Magnetic inductive devices can be found in many shapes and forms. The single most important aspect of their operation is that they need some kind of movement between the conductor coil and the magnetic field. In a normal situation we would think of induction taking place by the moving of a conductor across a stationary magnetic field or conversely a moving magnetic field across a stationary conductor.

Hall-Effect SensorWhen a chip of semi conductor material carrying a signal current across it is exposed to a
magnetic field, a small voltage called the “Hall voltage” is generated between the chip edges at 90 degrees to the path taken by the signal current. When the window is opened, the current does not flow. On the other hand, when the window shutters, the current can flow through chip to magnet.

  The hall voltage is supplied to the non-inverting side of a non-inverting op-amp which will switch high, supplying a voltage to the base of the NPN transistor. The transistor turns on pulling the signal out line to ground. As the magnet is interrupted and shielded the voltage is switched off and on to ground creating a square wave.

Optical Distributor

Reference by

http://www.autoshop101.com/

http://moodle.unitec.ac.nz/file.php/1310/Theory/Lesson_2_Sensors/Lesson_2_Sensors.pdf