A-6 Electrical ASE Test Preparation   


Red Kap Automotive Mechanics Clothing

Computer Sensors

1. Mass air flow sensors are used by the PCM (Engine Computer) to measure:

how fast air flows.
volumetric efficiency.
air density and volume.
humidity.

 

2. The Toyota MAP sensor is being tested for calibration accuracy. Technician A says that the signal voltage with the ignition switch on and the engine off should be between 3.3 and 3.9 volts when tested at sea level. Technician B says that if the signal voltage falls by the amount specified in the repair manual as a specific vacuum is applied to the sensor, then the sensor is good. Who is correct?

Technician A only.
Technician B only.
Both Technician A and B.
Neither Technician A nor B.

 

3. The MAP signal is used by the computer to determine:

mass air flow for air entering.
intake manifold pressure.
power inductance module.
W.O.T. power enrichment mode.

 

4. A hot-wire, mass air sensor measures:

airflow velocity entering the engine.
barometric absolute pressure.
air temperature in a turbocharged system.
molecular mass of air entering the engine.

 

 

5. The interval of time that each injector remains open is known as:

injector pulse width.
vacuum parameters.
intake manifold pressure.
open loop.

 

6. Referring to the Toyota schematic diagram below, a voltage check at the ECU connector THW (ECT- Engine Coolant Temperature Sensor) wire indicates 4.2 volts with a fully warmed up engine. What does this indicate?

Normal signal voltage for this engine temperature.
An excessively high resistance exists in the sensor or sensor circuit.
The sensor is shorted internally.
An accurate indication can only be determined if the value of the ECU pull-up resistor is known.

 

7. If a sub-O2 sensor on an engine is rapidly cycling between 200mV and 800mV, what would this indicate:

everything is normal.
the vehicle is in closed loop.
the catalytic converter has failed.
both the first two answers are correct.

 

8. The cam sensor provides information to the PCM (Engine Computer) in order to:

determine the engine RPM signal.
determine the crankshaft position information for injector and spark timing.
confirm that an ignition event has taken place.
both "a" and "b" are correct.

 

9. When testing an oxygen sensor, a good O2 will have a voltage range of:

0.000 volts to 1.200 volts.
0.100 volts to .450 volts.
0.200 volts to .800 volts.
0.450 volts to 1.000 volts.

 

10. A typical (Key On, Engine Off) KOEO from a Toyota MAP sensor at sea level will read approximately:

0.5v.
1.5v.
2.5v.
3.6v.

 

11. When a vacuum leak is created the oxygen sensor voltage should:

momentarily drop between .100 - .400 volts.
momentarily rise between .500 - .900 volts.
remain around .450 volts if the computer is functioning.
permanently rise between .500 - .900 volts. The O2 sensor will stop cycling.

 

12. A MAP Senor at idle should read approximately:

1.4v to 1.7v.
1.8v to 2.6v.
2.7v to 3.3v.
3.3v to 3.9v.

 

13. As the coolant temperature sensor (ECT) resistance drops below 1000 ohms?

it should be replaced.
it sets a code.
the mixture gets richer.
the mixture gets leaner.

 

14. Technician A says that an EGR position sensor is used to verify that the EGR has closed. Technician B says that an EGR position sensor is actually potentiometer.

Technician A only.
Technician B only.
Both Technician A and B.
Neither Technicians A nor B.

 

15. If this the picture below the Throttle Position Sensor (TPS), the computer would read this voltage and think the vehicle was:

at idle.
at cruise.
at W.O.T.
off.

 

16. Sensors that use a three wire and have a 5 volt reference are:

potentiometers.
resistors.
coolant and air temp sensors.
thermistors.

 

17. A zerconia exhaust gas oxygen (02) sensor is an example of a:

variable resistor.
potentiometer.
signal generator.
solenoid.

 

18. An engine detonation (knock) sensor uses a:

piezoresistive crystal.
voltage divider pickup.
potentiometer.
thermistor.

 

19. Engine detonation (knock) sensors produce what type of signal:

DC hertz.
digital.
AC sinewave.
pulse width.

  

20. Technician A says that the resistance of a PTC thermistor increases as the temperature increases. Technician B says that the resistance of an NTC thermistor decreases as temperature decreases. Who is correct?

technician A only.
technician B only.
both technicians A and B.
neither technicians A nor B.

    

21. Which of the following does not produce a digital signal?

Hall-Effect switches.
AC generators.
Optical sensors.
Microswitches.

  

22. Which of the following sensors directly measures engine load?

Coolant sensor (ECT).
Manifold absolute pressure sensor.
Throttle position sensor (TP).
Vehicle speed sensor.

  

23. The TPS at idle should read approximately:

0.7v to 1.2v.
1.2v to 2.0v.
3.3v to 3.9v.
5.0v.

  

24. Technician A says when testing an analog MAP sensor, as intake manifold pressure goes up (vacuum drops) the voltage should go up. Technician B says when testing an analog MAP sensor, as intake manifold vacuum goes up the voltage should go down. Who is correct?

technician A only.
technician B only.
both technicians A and B.
neither technicians A nor B.

 

25. Without an RPM signal to the computer on a fuel injected engine?

the system will go into backup mode.
the engine will run, but it will be sluggish.
the engine will start, but run very rich.
the engine will not run.

  

 

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