Make: Toyota
Model: 1ZZ-K10
Injector testing
Battery voltage: 14.12V
Fuel injector voltage: 14.08V
Discuss why would we bother checking the voltage supply to the fuel injectors.
The fuel injector contains an armature and a spring-loaded needle valve. When a certain voltage is applied to the solenoid coil, the armature is pulled in or pulled off. If there is no the supply voltage, the armature will not work. Therefore, the injector won't spray fuel.
If we find lower voltage at the injectors than at the battery, what can that mean? And how would injector operation be affected?
It could be faulty EFI relay, a bad wiring harness or faulty connections at the side of negative.
Negative trigger
TPS sensor
1: 4.995V
2: 0.001V
3: 0.611V
What is the purpose of the reference voltage to the throttle postion sensor?
If it does not receive reference voltage from ECU, the TPS can not deliver the proper signal.
In other words, if there is no fixed resistor between supply line and ground, a movable contact can not get a voltage relating to the resistance of the potentiometer.
What could cause problems so that there is not the correct reference voltage at the throttle position sensor?
loose connector
If there is a bad ground voltage reading(e.g above 0.5V), the TPS does not work properly.
Open the throttle to about the half open position. (2.298V)
Open the throttle to the full open postion (3.881V)
Describe how a TPS sensor works.
Throttle postion sensors are the potentiometer type sensors. The ECU uses their input to determine the amount of the throttle opening . Typical potentiometer is a variable resistance sensor with three terminals. One end of the resistor receives a reference voltage(5V), while the other end is grounded. The third terminal is attached to a movable contact that slides across the resistor to vary its resistance. The movable contact is connected to the throttle butterfly.
Discuss what type of sensor voltages should go to the ECU as the throttle is opened and closed.
When the throttle is opened, the sensor voltage increases. When the throttle is closed, the sensor voltage decreases.
WOT(Wide Open Throttle)- approximately 4.5V
Closed Throttle - approximately 0.5V
Describe problems which could occur to prevent the TPS from sending the correct voltage to ECU.
Due to overheating, inside of the TPS can be shorted or wiring harness shorted.
Loose connection or dirty connections also can be a problem to send correct voltage to ECU.
When there is a problem with a movable contact, it can cause a problem.Draw a full circuit diagram for the TPS on this vehicle.
ECT(Engine Coolant Temperature) Sensor
Make: LexusModel: ES300
Ignition "On", No starting
Measurement voltage: 1.192V
Ignition: On, Engine starting and after two minutes
Measurment Voltage: 0.711V
Good gound voltage testing
Measurment voltage: 0.037V
As shown above measurement, a warmer engine shows a lower voltage.
Describe how an ECT sensor works.
As shown below a circuit diagram, two resistors are connected in series. Therefore, when the water temperature is cold, the resistance of the second resistor is larger and more voltage is needed to push the electrons across the second resistor. When the water temperature is warm or hot, the resistance of the second resistor is smaller and less voltage is need to push the electrons across the second resistor.
Draw the circuit diagram for the ECT sensor for this vehicle. Include some detail inside the ECU.
Describe how the ECT sensor voltage affects the fuel injection output from the ECU.
When the engine is cold(sending 1.xx volts to ECU), the fuel mixture must be richer to prevent stalling and engine stumble. When the engine is warm(sending 0.xx volts to ECU), the fuel mixture can be leaner to provide maximum fuel economy and lower exhaust emissions.
Describe what could go wrong to creat an incorrect voltage for the ECU.
If the ECT has a poor wiring connection(high resistance), the ECU will supply a richer-than-normal fuel mixture based on the resistance of the ECT. Poor fuel economy can be caused by a defective sensor or high resistance in the sensor wiring. If the ECT was shorted and has too low resistance, the ECU will supply a leaner-than-normal fuel mixture. A too lean fuel mixture can cause driveability problems.
Why is it important to measure the ECU earth?
If there is a bad ground voltage reading, it affects the ECT signal sending to ECU and it affects the engine operation. (In here, the bad ground voltage is above 0.5V)
Discuss what could go wrong so that the ECU earth or gournd is not good.
If affects the reference voltage so the ECT would not send an incorrect signal to ECU.
MAP Sensor
Starting engine and idle: 0.458V(?)
Short acceleration: 1.1V(?)
Describe how MAP sensor works to tell the engine how much air comes into the engine.
The typical MAP sensor consists of a silicon wafer sealed on one side with a perfect vacuum and the other side is exposed to an intake manifold vacuum. There are four resistors attached to the silicon wafer which changes in resistance, when strain is applied to the wafer. The resistors are electrically connected to a wheatstone bridge circuit and then to a differential amplifer, which creates a voltage in proportion to the vacuum applied. At idle, a high vacuum is produced.(low pressure and less air coming in). So it produces a low voltage. When the engine starting to accelerate and the throttle is opened, the pressure inside the manifold rises(low vacuum and more air coming in). So it produces a high voltage.
What could go wrong so the ECU did not receive the correct signal from the MAP sensor?
If there is air leak around the hose, it can cause driveability problems(stalling, hesitation) and poor fuel economy. Also there can be other causes such as loose connection, defective silicon chip.
Draw the circuit diagram for the MAP sensor on this engine.
MAF Sensor
<MAF>
<IAT>
The mass air flow sensor measures the amount of air flowing through the throttle valve. There is a heated platinum wire which is exposed to the flow of the intake air. By applying a specific electrical current to the wire, the ECU heats it to a given temperature. The flow of incoming air cools both the wire and the internal thermistor. The voltage is proportional to the air flow through the sensor.
Typical idle sensor voltage is 1V.
Crankshaft Postion Sensor
Camshaft Postion Sensor
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