Ch. 73-75, 79-81, 76-78
typical TP sensor voltage at idle is about
0.5 volt or 10% of WOT sensor voltage
the IAT is being tested. after the vehicle has been allowed to cool for several hours, a scan tool is used to observe the IAT, and compare it to the engine coolant temperature (ECT). The two temperatures should be within how many degrees F of each other
5
the fuel injectors used on a gasoline direct injection system are pulsed using what voltage
50-90 V
which of these is the fuel pump
D
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
both b and c are possible: the TP sensor signal is shorted to 5 volt reference and the TP sensor is shorted
a lack of power from an engine equipped with gasoline direct injection could be due to
both b and c: carbon on the injectors and carbon on the intake valves
a P0102 DTC is being discussed. tech a says that sensor circuit shorted to ground can be the cause. tech b says that an open sensor voltage supply circuit could be the cause. who's right
both techs
tech a says that MAP sensors use a 5 volt reference voltage from the PCM. tech 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's right
both techs
tech a says that fuel pressure regulators are often located on the return side of the fuel rail. tech b says that the fuel pressure regulator is located at the fuel tank on vehicles using mechanical returnless systems. who's right
both techs
tech a says that most fuel injection systems use the PCM to control the pulsing of the fuel injectors. tech b says that most fuel injection systems use the PCM to control the operation of the fuel pump relay. which tech is correct
both techs
which sensor has the greatest influence on injector pulse width besides the MAF sensor
TP
a typical TP sensor registers about how many volts at WOT (wide open throttle)
4.5
GDI fuel injectors operate under a pressure of about
500-2900 PSI
the first fuel filter in the sock inside the fuel tank normally filters particles larger than
70-100 microns
which statement is false
Absolute pressure is equal to barometric pressure plus intake manifold vacuum
which sensor is used to measure manifold vacuum
MAP
the sensor that measures the temperature of the air being drawn into the engine is called a(n)
both a and b: NTC thermistor and IAT
as the load on an engine increases manifold vacuum decreases and the manifold absolute pressure
increases
if it tripped, which type of safety device keeps the electric fuel pump from operating
inertia switch
the 4 basic computer functions include
input, processing, storage, and output
where is the fuel pump located on most vehicles today
inside the fuel tank
what determines the amount of fuel injected when an injector opens
length of time the injector is open
all of the following are disadvantages of gasoline direct injection EXCEPT
less need for extra fuel for acceleration
when the fuel pressure regulator is deactivated, the fuel pressure defaults to
low pressure mode
refer to this diagram of a fuel pump control circuit. what type of a driver is used in this circuit
low-side driver circuit
which of these is NOT a purpose or function of the MAP sensor
measures engine speed
what type of circuit is shown in this schematic
negative temperature coefficient (NTC) thermistor circuit
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. tech a says this is the signal voltage and is a little slow. tech b says the TP sensor ground circuit has excessive resistance. who's right
neither techs
what prevents the fuel pump inside the fuel tank from catching the gasoline on fire
no air is around the motor brushes
when testing the ECT sensor with the disconnected, the technician should select what position on the DMM
ohms
which one of these seniors is NOT used to determine injector pulse width during open loop mode
oxygen sensor
dampeners are used on some fuel rails to
reduce noise
why are some fuel rails rectangular in shape
reduces noise
when testing a MAP sensor, the tech should first check the ____ voltage
reference
GDI high pressure fuel lines must be _____ once they are removed for service
replaced
which type of port fuel injection fires each injector separately, following the engine firing order
sequential fired
which wire on a typical TP sensor should back probed to check the voltage signal to the PCM
signal wire
which type of port fuel injection fires all the injectors at the same time, once per crankshaft revolution
simultaneous double fired
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(n) _____ 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 type of device is used in a typical idle air control
stepper Motor
all of the following are approved methods or tools used when diagnosing an ECT (engine coolant temperature) sensor EXCEPT
substituting a variable resistor
which term is used to describe a TBI system where the injector pulses once per distributor reference pulse
synchronized
tech a says that fuel filters aren located in the fuel supply line. tech b says that fuel filters are located in the fuel return line. which tech is correct
tech a
tech a says that a MAP sensor can be tested by visual inspection using a digital meter, or a scan tool. tech b says a light engine load results in low intake manifold vacuum and a high MAP sensor signal voltage
tech a only
tech a says that fuel tank accident and rollover protection devices include check values and inertia switches. tech b says that most fuel lines are made of ABS plastic.m who's right
tech a only
a _____ is a variable resistance sensor with 3 terminals
potentiometer
what type of sensor is used to measure the position of the throttle
potentiometer
What unit of electricity is used as a signal for a computer?
volt
GDI equipped engines have a higher efficiency due to a ____ compression ratio
higher
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 degree f
the "brain" of the computer is the
CPU
most TP sensors have how many wires
3
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
all OBDII vehicles use what type of read-only memory
EEPROM
the MAP sensor is used by the PCM to diagnose the _____ system
EGR
a TP sensor is what type of sensor
Potentiometer
which of these tools would be used to test a MAP sensor
a digital voltmeter
a typical MAP sensor compares the vacuum in the intake manifold to
a perfect vacuum
a GDI system operating in stratified mode results in
a rich air fuel mixture near the spark plug tip
which item is a computer input sensor
all of the above: engine coolant temperature, rpm, throttle position angle
which item is a computer output device
all of the above: fuel injector, evaporative emission control solenoid, transmission shift solenoid
the high pressure fuel pump pressure is regulated by using
an electric pressure control valve
most MAP sensors produce what type of output signal
analog DC volage (DCV)
analog signals from sensors are changed to digital signals for processing by the computer through which type of circuit
analog-to-digital converter
where is the fuel pressure regulator located on a vacuum biased port fuel injection system
at the outlet of the fuel rail
when the engine is at idle speed, manifold vacuum is
high (17 to 21 in. Hg)
tech a says that the ECT and IAT sensors can be tested visually, as well as by using a digital multimeter or a scan tool. tech b says that the ECT sensor is a high-authority sensor at engine start up and is used for open loop control, as well as idle speed. who is right
both techs
tech a says that the fuel pump relay is usually controlled by the PCM. tech b says that a TBI injector squirts fuel above the throttle plate. which tech is correct
both techs
tech a says that the purpose of the IAT sensor is to provide the engine computer (PCM) with the temperature of the air entering the engine. tech b says that the IAT sensor information is used for fuel control (adding or subtracting fuel) and spark timing, depending on the temperature of incoming air. who is right
both techs
tech a says that vehicles with electronic returnees fuel systems are pulse width modulation to power the fuel pump and maintain fuel pressure. tech b says that the electric returnees fuel system uses a power transistor to control the fuel pump. whose right
both techs
which term describes the PCM shutting off fuel injection when the accelerator all the way down
clear flood mode
computer speed is measured in
clock speed (Hz)
the TP sensor affects the operation of all of these, EXCEPT
correcting for rich and lean air fuel mixture
the amperage draw of an electric fuel pump is higher that specified. all of the following are possible causes EXECPT
corroded electrical connections at the pump motor
the amperage draw of an electric fuel pump is lower than specified. what is the most likely cause?
corroded electrical connections at the pump motor
all of the following are advantaged of gasoline direct injection EXCEPT
decreased throttle response
as the altitude of the vehicle increases, BARO voltage
decreases
an engine fuel temperature (EFT) sensor is used on some vehicles, since fuel temperature changes the ___ of the fuel
density
where is the fuel injected in an engine equipped with gasoline direct injections
directly into the combustion chamber
the ratio of on time relative to the period of the complete cycle is the
duty cycle
which of these sensors does that TP sensor back up if the PCM determines that a failure has occured
either b or c: MAP sensor and MAF sensor
a small amount of gasoline in the regulator vacuum hose is normal on older vehicles
false
where is the electric fuel pump is usually mounted
fuel tank
tech a says that other temperature sensors that operate like the ECT include transmission fluid temperature (TFT) and engine oil temperature sensors. tech b says that all temperature sensors increase in resistance as the temperature decreases. who is right
tech a only
tech a says that pressure below atmospheric pressure is called vacuum and is measured in inches of mercury (Hg). tech b says that a manifold absolute pressure (MAP) sensor uses a low vacuum in the sensor to determine the pressure. who's right
tech a only
tech a says that the 3 wires of the TP sensor include a 5 volt reference voltage from the PCM. tech b says that a TP sensor is a 3 wire variable resistor called a rheostat. who is right
tech a only
tech a says that vacuum operated fuel pressure regulators maintain an equal drop across the fuel injectors all the time. tech b says that intake manifold pressure is high at idle. who's right
tech a only
two techs are discussing MAP sensors. tech a says that the MAP sensor should be replaced if anything comes out of the sensor when the vacuum hose is removed from the sensor. tech b says that the injector pulse width should increase when vacuum to the MAP sensor is increased. who's right
tech a only
tech a says that the TP sensor signal voltage should be about 0.5 volts at idle and increases to about 2.5 volts at wide open throttle (WOT). tech b says a TP sensor can be tested using DMM or a scan tool. who's right
tech b
a MAP sensor is being discussed. tech a says that many MAP sensors act as a barometric pressure sensor when the ignition switch is turned off. tech b says that on many MAP sensors the signal voltage should increase when the vacuum at the sensor decreases. who's right
tech b only
tech a says that a heavy engine load results in high intake manifold vacuum and a high MAP sensor signal voltage. tech b says that a manifold absolute pressure (MAP) sensor uses a perfect vacuum (zero absolute pressure) in the sensor to determine the pressure. who's right
tech b only
tech a says that the 3 wires on the TP sensor include a 5 volt reference voltage from PCM plus the signal wire to PCM and a ground to the engine block. tech b says that the TP sensor is used by the PCM to determine torque converter engagement and transmission shift points. who's right
tech b only
two techs are discussing the IAT sensor. tech a says that the IAT sensor is more important to the operation of the engine (higher authority) than the ECT sensor. tech b says that the PCM adds fuel if the IAT indicated that the incoming air temperature is cold. who's right
tech 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
why is a vacuum line attached to a fuel pressure regulator on many port fuel engines
to create an equal pressure drop across the injectors
what two things can a vehicle computer actually perform (output)
turn something on or turn something off
a scan tool can be used to test a MAP sensor by monitoring the injector pulse width (in milliseconds) while _____ nis being applied to the MAP sensor
vacuum