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
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
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.
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 % |
Good work Kim, maybe would of been better if you added more discussion on good vs bad readings. And also added a couple more worksheets (this post is a bit short)
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