ep 2
When checking the ECT sensor with a scan tool, about what temperature should be displayed if the connector is removed from the sensor with the key on, engine off?
-40°F (-40°C)
Cycles per second are expressed in ________.
Hertz
GMLAN is the General Motors term for which type of module communication?
High-speed CAN
Which type of sensors uses a burn-off circuit?
Hot wire MAF sensor
A module is also known as a ________.
Node
Which terminal of the OBD-II data link connector is the signal ground for all vehicles?
5
UART uses a signal that toggles between 0 volts and ________.
5 volts
GDI fuel injectors operate under a pressure of about ________.
500 to 2,900 PSI
A typical IAT or ECT sensor reads about 3000 ohms when tested using a DMM. This resistance represents a temperature of about ________.
70° F (20° C)
A wide band oxygen sensor heater can draw how much current (amperes)?
8 to 10 A
Oscilloscopes use what type of lead connector?
BNC
Technician A says that a MAF sensor actually measures the density and amount of air flowing into the engine. Technician B says a that hot wire MAF sensor uses the electronics in the sensor itself to heat wire 70°C above the temperature of the air ntering the engine. Who is right?
Both
A P0102 DTC is being discussed. Technician A says that a sensor circuit shorted-to-ground can be the cause. Technician B says that an open sensor voltage supply circuit could be the cause. Who is right?
Both technicians A and B
The throttle plate actuator motor is what type of electric motor?
DC motor
Air that enters the engine without passing through the air flow sensor is called ________.
False air
Which item is a computer output device?
Fuel injector Transmission shift solenoid Evaporative emission control solenoid All of the above
A digital meter that can show waveforms is a ________
GMM
An oscilloscope display is called a ________.
Graticule
The throttle position sensor used in the throttle body assembly of an electronic throttle control (ETC) system is what type?
Two potentiometers that read in the opposite direction A Hall-effect sensor Either B or C
Which sensor has a switch that controls the electric fuel pump?
VAF
A scan tool can be used to test a MAP sensor by monitoring the injector pulse width (in milliseconds) while is being applied to the MAP sensor.
Vacuum
What component pulses the fuel injector on most vehicles?
Powertrain control module (PCM)
A fuel injection system that does not use a sensor to measure the amount (or mass) of air entering the engine is usually called a(an) ________ type of system
Speed density
Which fuel-injection system uses the MAP sensor as the primary sensor to determine the base pulse width?
Speed density
What are the two methods of sensing incoming engine air flow?Select one:a. Speed density and throttle position. Speed density and mass air flow. EGR and positive crankcase ventilation. Mass air flow and air intake
Speed density and mass air flow
If the throttle plate needs to be cleaned, what symptoms will be present regarding the operation of the engine?
Stalls Rough idle Hesitation on acceleration Any of these
What type of device is used in a typical idle air control?
Stepper motor
Which mode of operation results in a richer air-fuel mixture near the spark plug?
Stratified
Which sensor has the greatest influence on injector pulse width besides the MAF sensor
TP
Which sensor is generally considered to be the electronic accelerator pump of a fuel-injected engine?
TP sensor
Technician A says that a MAP sensor can be tested by visual inspection, using a digital meter, or a scan tool. Technician B says a light engine load results in low intake manifold vacuum and a high MAP sensor signal voltage. Who is right?
Tech A
Technician A says that a MAP sensor can be tested by visual inspection, using a digital meter, or a scan tool. Technician B says a light engine load results in low intake manifold vacuum and a high MAP sensor signal voltage. Who is right?
Tech A
Which type of port fuel-injection system uses a fuel temperature and/or fuel-pressure sensor?
Electronic returnless systems
The actuator motor is controlled by the PCM through what type of circuit?
H-bridge
The SAE term for the vehicle computer is ________.
PCM
A TP sensor is what type of sensor?
Potentiometer
Voltage signals (waveforms) that do not go below zero are called ________.
Pulse trains
Which item is a computer input sensor
RPM Throttle position angle Engine coolant temperature All of the above
Dampeners are used on some fuel rails to ________.
Reduce noise
Why are some fuel rails rectangular in shape?
Reduces noise
Port fuel-injection systems generally use what type of injector driver?
Saturated switch
which type of port fuel injection fires each injector separately, following the firing order
Sequential fired
Which wire on a typical TP sensor should back-probed to check the voltage signal to the PCM?
Signal wire
In a typical port fuel injection system, which injectors are most subject to becoming restricted?
The injectors at the end of the rail on a returnless system The injectors at the bends in the rail Either B or C
With the ignition off and the key out of the ignition, what should happen if a technician uses a screwdriver to gently push on the throttle plate in an attempt to open the valve?
The throttle should move, and then spring back to the home position when released.
Why is a vacuum line attached to a fuel-pressure regulator on many port-fuel-injected engines?
To create an equal pressure drop across the injectors
A gasoline direct injection system can be used to start an engine without the need for a starter.
True
Some engines that use a gasoline direct injection system also have port injection.
True
What two things can a vehicle computer actually perform (output)?
Turn something on or turn something off
what test is being performed here
injector resistance
A wide band oxygen sensor was first used on a Honda in what model year?
1992
Which terminal of the data link connector does General Motors use for Class 2 communication?
2
Most TP sensors have how many wires?
3
The typical MAF reading on a scan tool with the engine at idle speed and normal operating temperature is ________.
3 to 7 grams per second
Most port fuel-injected engines operate on how much fuel pressure?
35 to 45 psi (240 to 310 kPa)
A vehicle runs fine when in reverse yet has a rough idle and stalling when put in drive. This could be caused by ________.
A cracked air inlet hose
A green wrench symbol is displayed on the dash. What does this mean?
A fault in the ETC in a Ford has been detected.
A low O2S voltage could be due to ________.
A lean exhaust A defective spark plug wire Both B and C
typical MAP compares the vacuum in the intake manifold to ________.
A perfect vacuum
A high O2S voltage could be due to _____
A rich exhaust
Which airflow sensor has a dampening chamber?
A vane airflow sensor
Where is the fuel-pressure regulator located on a vacuum-biased port fuel-injection system?
At the outlet of the fuel rail
Throttle-body fuel-injection systems use what type of injector driver
Peak and hold
A wide band oxygen sensor needs to be heated to what operating temperature?
1,400 deg. F
An oxygen sensor is being tested using a digital storage oscilloscope (DSO). A good oxygen sensor should display how many switches per second?
1-5
A throttle position sensor waveform is going to be observed. At what setting should the volts per division be set to see the entire waveform from 0 volts to 5 volts?
1.0 V/Div
A wide band oxygen sensor is capable of detecting the air-fuel mixture in the exhaust from ________ (rich) to ________ (lean).
10:1 to 23:1
The MAF sensor on a General Motors 3800 V-6 is being tested for contamination. Technician says that the sensor should show over 100 grams per second on a scan tool display when the accelerator is depressed to WOT (wide open throttle) on a running engine. Technician B says that the output frequency should exceed 7000 Hz when the accelerator pedal is depressed to WOT on a running engine. Who is right?
Both technicians A and B
The fuel pressure drops rapidly when the engine is turned off. Technician A says that one or more injectors could be leaking. Technician B says that a defective check valve in the fuel pump could be the cause. Which technician is correct?
Both technicians A and B
Two technicians are discussing testing MAP sensors. Technician A says that the MAP sensor voltage on a General Motors vehicle at idle should be about 1.0 volt. Technician B says that the MAP sensor frequency on a Ford vehicle at idle should be about 105—108 Hz. Which technician is correct?
Both technicians A and B
If the transmission fluid temperature (TFT) sensor indicates cold automatic transmission fluid, what would the PCM do to the shifts?
Delayed shift points and torque converter clutch disabled
Where is the fuel injected in an engine equipped with gasoline direct injection?
Directly into the combustion chamber
As the load on an engine increases, manifold vacuum decreases and the manifold absolute pressure ________.
Increases
What happens to the voltage measured at the ECT sensor when the thermostat opens?
Increases slightly
The four basic computer functions include ________.
Input, processing, storage, and output
Which of these sensors does the TP sensor back up if the PCM determines that a failure has occurred?
MAF sensor MAP sensor Either B or C
what sesnor is used to measure manifold vaccum
MAP
Which of these is NOT a purpose or function of the MAP sensor?
Measures engine speed
When testing the ECT sensor with the connector disconnected, the technician should select what position on the DMM?
Ohms
A signal showing the voltage of a battery displayed on a digital storage oscilloscope (DSO) is being discussed. Technician A says that the display will show one horizontal line above the zero line. Technician B says that the display will show a line sloping upward from zero to the battery voltage level. Which technician is correct?
Technician A only
Technician A says that an analog scope can store the waveform for viewing later. Technician B says that the trigger level has to be set on most scopes to be able to view a changing waveform. Which technician is correct
Technician B only
Two technicians are discussing the IAT sensor. Technician A says that the IAT sensor is more important to the operation of the engine (higher authority) than the ECT sensor. Technician B says that the PCM will add fuel if the IAT indicates that the incoming air temperature is cold. Who is right?
Technician B only
After a TP sensor has been tested using the min/max function on a DMM, a reading of zero volts is displayed. What does this reading indicate?
The TP sensor is open at one point during the test
On a vehicle with a speed density fuel injection system, which of the following is likely to occur with a vacuum leak?
all of these
Technician A says that an oxygen sensor can have one, two, three, four, or more wires, depending on the style and design. Technician B says that if the exhaust has little oxygen, the voltage of a conventional Nernst cell oxygen sensor will be close to 1 volt (1000 mV) and close to zero if there is high oxygen content in the exhaust. Who is right?
both
which term describes the PCM using oxygen sensor feedback to control fuel delivery
closed loop mode
The voltage output of a zirconia oxygen sensor when the exhaust stream is lean (excess oxygen) is ________.
relatively low (close to 0 volt)
When the ignition is first turned on a click noise is heard from under the hood of a vehicle equipped with ETC. Technician A says that this is the normal operation of the ETC self-test. Technician B says that the TAC motor should not move unless the engine is running. Which technician is correct?
tech a
All OBDII vehicles use what type of read-only memory?
EEPROM
The frequency output of a digital MAP sensor is reading 114 Hz. What is the approximate engine vacuum?
15 in. Hg
The throttle plate is spring loaded to hold the throttle slightly open how far?
16% to 20%
Terminal 16 of the OBD-II data link connector is used for what?
12 volts positive
GM Class 2 communication toggles between ________.
0 and 7 volts
Typical TP sensor voltage at idle is about ________.
0.5 volt or 10% of WOT sensor voltage
The fuel pump inside the fuel tank on a vehicle equipped with gasoline direct injection produces about what pressure?
50 to 60 PSI
The fuel injectors used on a gasoline direct injection system are pulsed on using what voltage?
50 to 90 V
Setting the time base to 50 ms per division will allow the technician to view a waveform how long in duration?
500 ms
A high-speed CAN BUS communicates with a scan tool through which terminal(s)
6 and 14
Which statement is FALSE?
Absolute pressure is equal to barometric pressure plus intake manifold vacuum
The use of an electronic control (ETC) system allows the elimination of all of these EXCEPT ________.
Accelerator pedal
What does the post, or downstream, oxygen sensor (HO2S) measure?Select one:
Amount of oxygen behind the catalytic converter
The high-pressure fuel pressure is regulated by using ________
An electric pressure control valve
Fuel injectors can be tested using ________.
An ohmmeter A stethoscope An oscilloscope Any of these
Analog signals from sensors are changed to digital signals for processing by the computer through which type of circuit?
Analog-to-digital converter
A P0107 DTC is being discussed. Technician A says a that defective MAP sensor could be the cause. Technician B says that a MAP sensor signal wire shorted-to-ground could be the cause. Who is right?
Both technicians A and B
A P0133 DTC is being discussed. Technician A says that a defective heater circuit could be the cause. Technician B says that a contaminated sensor could be the cause. Which technician is correct?
Both technicians A and B
Fuel injection service is being discussed. Technician A says that the throttle plate(s) should be cleaned.Technician B says that the fuel rail should be cleaned. Which technician is correct?
Both technicians A and B
Technician A says that MAP sensors use a 5-volt reference voltage from the PCM. Technician B says that the MAP sensor voltage will be higher at idle at high altitudes compared to when the engine is operating at near sea level. Who is right?
Both technicians A and B
Technician A says that module communications networks are used to reduce the number of wires in a vehicle. Technician B says that a communications network is used to share data from sensors, which can be used by many different modules. Who is right?
Both technicians A and B
Technician A says that the fuel pump relay is usually controlled by the PCM. Technician B says that a TBI injector squirts fuel above the throttle plate. Which technician is correct?
Both technicians A and B
CAN H and CAN L operate how?
CAN H is at 2.5 volts when not transmitting CAN L is at 2.5 volts when not transmitting CAN H goes to 3.5 volts when transmitting All of the above
The "brain" of the computer is the ________
CPU
Which design of MAP sensor produces a frequency (digital) output signal?
Capacitor-capsule
A lack of power from an engine equipped with gasoline direct injection could be due to ________.
Carbon on the injectors Carbon on the intake valves Both B and C
The throttle body may be cleaned (if recommended by the vehicle manufacturer) if what conditions are occurring?
Coast-down stall Rough idle Lower-than-normal idle speed Any of the above
When measuring the output signal of a MAP sensor on a General Motors vehicle, the digital multimeter should be set to read ________.
DC volts
When testing an ECT sensor on a vehicle, a digital multimeter can be used and the signal wires back probed. What setting should the technician use to test the sensor?
DC volts
The sensor that most determines fuel delivery when a fuel injected engine is first started is the ________.
ECT sensor
A technician attaches one lead of a digital voltmeter to the ground terminal of the TP sensor and the other meter lead to the negative terminal of the battery. The ignition is turned on, engine off, and the meter displays 37.3 mV. Technician A says this is the signal voltage and is a little low. Technician B says the TP sensor ground circuit has excessive resistance. Who is right?
Neither technician A nor B
The vacuum hose from the fuel-pressure regulator was removed from the regulator and gasoline dripped out of the hose. Technician A says that this is normal and that everything is okay. Technician B says that one or more of the injectors may be defective, causing the fuel to get into the hose. Which technician is correct?
Neither technician A nor B
Two technicians are discussing Karman Vortex sensors. Technician A says that they contain a burn-off circuit to keep them clean. Technician B says that they contain a movable vane. Which technician is correct?
Neither technician A nor B
A technician is checking the operation of the electronic throttle control system by depressing the accelerator pedal with the ignition in the on (run) position (engine off). What is the most likely result if the system is functioning correctly?
No throttle movement
An oxygen sensor is being tested with a digital multimeter using the MIN/MAX function. The readings are: minimum = 78 mV; maximum = 932 mV; average = 442 mV. Technician A says that the engine is operating normally. Technician B says that the oxygen sensor is skewed too rich. Which technician is correct?
Technician A only
Two technicians are diagnosing a poorly running engine with no stored DTCs. When the MAF sensor is unplugged, the engine runs better. Technician A says that this means the MAF is supplying incorrect air flow information to the PCM. Technician B says that this indicates the PCM is defective. Who is right?
Technician A only
Two technicians are discussing the DC coupling setting on a DSO. Technician A says that the position allows both the DC and AC signals of the waveform to be displayed. Technician B says that this setting allows just the DC part of the waveform to be displayed. Which technician is correct?
Technician A only
A P0118 DTC is being discussed. Technician A says that the ECT sensor could be shorted internally.Technician B says that the signal wire could be open. Who is right?
Technician B only
Technician A says that the port fuel injection injectors operate using five volts from the computer. Technician B says that sequential fuel injectors all use a different wire color on the injectors. Which technician is correct?
Technician B only
Two technicians are discussing a stepped ECT circuit. Technician A says that the sensor used for a stepped circuit is different from the one used in a non-stepped circuit. Technician B says that a stepped ECT circuit uses different internal resistance inside the PCM. Who is right?
Technician B only
After a TP sensor has been tested using the min/max function on a DMM, a reading of 5 volts is displayed.What does this reading indicate?
The TP sensor signal is shorted to 5-volt reference
A P0122 DTC is retrieved using a scan tool. This DTC means ________.
The TP sensor voltage is low The TP sensor could be shorted-to-ground The TP sensor signal circuit could be shorted-to-ground All of the above are correct
The high-pressure fuel pump used in gasoline direct injection (GDI) systems is powered by ________.
The camshaft
What unit of electricity is used as a signal for a computer?
Volt
When does the PCM perform a self test of the ETC system?
When the ignition switch is first rotated to the on position, before the engine starts
Technician A says that fuel pressure regulators are often located on the return side of the fuel rail. Technician B says that the fuel pressure regulator is located at or near the fuel tank on vehicles using mechanical returnless systems. Which technician is correct?
both