Chapter 73-76 and 78 engine repair
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 eachother?
5
The throttle position sensor is an output component
False
technician A says taht 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
All of the following are approved methods for diagnosing an ECT sensor except____
Substituting a variable resistor
Which of these components lets the PCM know how fast you want to accelerate?
TP (throttle position) sensor
which sensor is generally considered to be the electronic accelerator pump of a fuel-injected engine?
TP sensor
a typical TP sensor registers about how many volts at WOT?
4.5
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)
Which computer component generates a steady stream of one-bit long voltage pulses?
Clock generator
Computer speed is measured in____
Clock speed (Hz)
What happens to the voltage measured at the ECT sensor when the thermostat opens?
Increases slightly
Which computer function is defined as a voltage signal from a sensor or switch?
Input
The four basic computer functions include____
Input, processing, storage, and output
Refer to this diagram of a fuel pump control circuit. What type of a driver circuit is used in this circuit *diagram*
Low-side driver circuit
Which sensor is used to measure manifold vacuum?
MAP
which of these sensors does the TP sensor back up if the PCM determines that a failure has occurred?
MAP or MAF sensor (either B or C)
The sensor that measures the temperature of the air being drawn into the engine is called a(n)
NTC and PTC thermistor (both a and b)
What type of circuit is shown in this schematic?
Negative temperature coefficient (NTC) thermistor circuit
two technicians are discussing testing MAP sensors. Technician A says that the MAP sensor voltage on a genreal 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
as the load on an engine increases, manifold vacuum decreases and the manifold absolute pressure (MAP) _____
increases
which of these is NOT a purpose or function of the MAP sensor?
measures engine speed
A technician attaches one lead of a digital voltmeter tot eh ground terminal of the TP sensor and the other meter to 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 or b
This GM ECT sensor is being tested. The ambient temperature is 90°F. This sensor is____
out of specification
A TP sensor is what type of sensor?
potentiometer
A ____ is a variable-resistance sensor with three terminals
potentiometer
The third terminal of a potentiometer is attached to a movable contact that slides across the resistor to vary ____.
resistance
which wire on a typical TP sensor should back-probed to check the voltage signal to the PCM?
signal wire
Which item is a computer output device?
Evaporative emission control solenoid, fuel injector, and transmission shift solenoid (all of the above)
A fuel injector can be an input or an output component
False
The SAE term for the vehicle computer is ____
PCM
Analog signals from sensors are changed to digital signals for processing by the computer through which type of circuit?
Analog-to-digital converter
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 or C)
typical TP sensor voltage at idle is about ___
.5 volt or 10% of WOT sensor voltage
what voltage will be measured at terminal C as shown *insert random diagram*
.5 volts
the frequency output of a digital MAP sensor is reading 114 Hz. What is the approximate engine vacuum?
15 in. Hg
Most TP sensors have how many wires?
3
Which term describes the speed of data transmission?
Baud rate
Which data set contains only two digits
Binary
Technician A says that the purpose of the IAT sensor is to provide the engine computer (PCM) with the temperature of air entering the engine. Technician 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 technicians A and B
The "brain" of the computer is the ____
CPU
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
when measuring the output signal of a MAP sensor on a general motors vehicle, the digital mulitmeter should be set to read ____
DC volts
If the transmission fluid temperature sensor indicated cold automatic transmission fluid, what would the PCM do to the shifts?
Delayed shift points and torque converter clutch disabled
The ratio of on time relative to the period of the complete cycle is the____
Duty cycle
The sensor that most determined 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
Which components contains the information in the computer That is specific to the particular model vehicle?
EEPROM
Which term describes the process of manually adjusting variables such as speed, load, and spark timing to determine the optimum output settings for the computer?
Engine mapping
When testing the ECT sensor with the connector disconnected, the technician should select what position on the DMM?
Ohms
Which computer function describes how the computer handles inputs?
Process
Which item is a computer input sensor?
RPM, Throttle position angle, and engine coolant temperature (all of the above)
A P0117 DTC is being discussed. Technician A says that the ECT sensor could be internally shorted to ground. Technician B says that the signal wire could be open. Who is right?
Technician A only
Technician A says that the other temperature sensors operate like the ECT include transmission fluid temperature and engine oil temperature sensors. Technician B says that all temperature sensors increase in resistance as the temperature decreases. Who is right?
Technician A only
A P0118 DTC is being discussed. Technician A days 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 days that the ECT and IAT can be tested visually, as well as by using a digital multimeter or a scan tool. Technician B says that the ECT sensor is a high-authority sensor at engine start-up and is used for an open-loop control, as well as idle speed. Who is right?
Technician B only
Technician A says that temperature sensors decrease in resistance as the temperature increases; this is called positive temperature coefficient (PTC). Technician B says that some vehicle manufacturers use a stepped ECT circuit inside the PCM to broaden the accuracy of the sensor. Who is right?
Technician B only
Technician A says that the TP sensor signal voltage should be about .5 volt at idle and increase to about 2.5 volts at wide-open throttle (WOT). Technician B says A TP sensor can be tested using a DMM, DSO, or scan tool. Who is right?
Technician B only
Technician A says that the three wires on the TP sensor include a 5-volt reference voltage from PCM, Plus the signal wire to PCM, and a ground wire to the engine block. Technician B says that the TP sensor is used by the PCM to determine torque converter engagement and transmission shift points. Who is right?
Technician B only
Two technicians are discussing a stepped ECT circuit. Technician A days 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
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?
That the TP sensor is open at one point during the test
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?
That the TP sensor is shorted or the TP sensor signal is shorted to a 5-volt reference.
A P0122 DTC is retrieved using a scan tool. This DTC means ____
The TP sensor signal circuit could be shorted-to-ground The Tp sensor voltage is low The TP sensor could be shorted-to-ground (all of the above)
What two things can a vehicle computer actually perform (output)?
Turn something on or turn something off
What unit of electricity is used as a signal for a computer?
Volt
a typical MAP compaeres the vacuum in the intake manifold to ____
a perfect vacuum
which statement is false?
absolute pressure is equal to barometric pressure plus intake manifold vacuum
which design of MAP sensor produces a frequency (digital) output signal?
capacitor-capsule
The TP sensor affects the operation of all of these, except____.
correcting for rich and lean air-fuel mixtures
the torque converter clutch will release when any movement of the TP sensor is detected
false
Technician A says that the 3 wires on the TP sensor include a 5-volt reference voltage from the PCM. Technician B says that a TP sensor is a three-wire variable resistor called a rheostat. Who is right?
technician A
A P0113 DTC is being discussed. Technician A says that the IAT sensor could be internally (electrically) shorted. Technician B says that the PCM could be defective. Who is right?
technician B only
