Deck 25: Detailed Diagnosis and Sensors

Question 1

Mode 6 data are the results of the monitor diagnostic tests.

Answer 1

True

Question 2

A technician is setting up a lab scope to measure a sensor. Technician A says that the vertical voltage scale must be adjusted in relation to the expected voltage signal. Technician B says the trigger slope must be set to positive if the trace begins with a rising voltage. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Answer 2

C

Question 3

Which statement is NOT true?

A) Some sensors are voltage or frequency generators
B) Some sensors are variable resistors
C) Some sensors are simple on-off switches
D) Some sensors are solenoids

Answer 3

D

Question 4

A vehicle with a DTC for an engine coolant temperature out of range code is being tested. The serial data stream shows the coolant temperature to be 198 degrees Fahrenheit. When the technician tests the resistance between the ETC terminals, he finds infinite resistance. The specifications call for 20 to 40 ohms at 200 degrees Fahrenheit. After the ECT is replaced and the code is erased, the system runs normally and the code and MIL illumination do not reoccur. How is this possible?

A) There was excessive air in the cooling system; when the ECT sensor was removed, the trapped air bled out
B) The ETC code was set by a loose connection where the harness meets the ECT terminals; disconnecting and reconnecting the plug essentially fixed the problem
C) The problem is an intermittent electrical fault; it will eventually reoccur
D) When the ECT failed, the PCM substituted a nominal ECT value that allowed the engine to run in limp home mode; the substituted value was displayed by the scan tool

Question 5

The resistance of the intake air temperature (IAT) sensor increases as air temperature increases.

Question 6

Trouble codes are being discussed. Technician A says that the first time the system detects a fault, a pending code is set. Technician B says that a pending code will turn on the MIL light. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 7

For most actuators, the circuit driver in the PCM applies a ground to the circuit to turn the actuator on and removes the ground to turn the actuator off.

Question 8

A sensor with a bad ground connection will produce a lower than normal signal voltage.

Question 9

If the MIL light is ON, there will be a DTC and associated freeze frame data stored in the PCM's memory.

Question 10

Which of the following tools is NOT used in testing engine sensors?

A) DMM
B) test light
C) scan tool
D) lab scope

Question 11

The sensor and output status data stored when a DTC is set is called ______.

A) snap shot data
B) freeze frame data
C) mode 6 data
D) failure record

Question 12

Because air/fuel ratio sensors produce a signal only after their current output has been processed by the PCM, they cannot be tested with a voltmeter or lab scope.

Question 13

On some vehicles, actuators can be tested with a scan tool by accessing output state control (OSC) or output test mode (OTM). In this mode, the actuator enabled or disabled, or the duty cycle increased or decreased.

Question 14

The engine coolant temperature sensor is typically found in the radiator.

Question 15

The device that protects the PCM and other electronic components from the voltage spike created in the windings of a solenoid, relay, or magnetic clutch when they are turned off is called a ______.

A) filter choke
B) clamping diode
C) suppression capacitor
D) voltage divider

Question 16

Some PCM inputs come from another control module through the vehicle network.

Question 17

A vehicle towed into the shop with a "cranks but doesn't start" problem. A quick check under the hood reveals that the spark plugs are not firing and the injectors are not receiving a pulse from the PCM. The technician notices that the MIL light does not come on when the key is turned to the run position. What would you do next?

A) Check the PCM's fuses, power wires, and ground wires
B) Replace the PCM
C) Check the main power relay in the power distribution center
D) Check for codes with a scan tool

Question 18

Two technicians are discussing OBD-II monitor readiness status. Technician A says that the vehicle must be driven through a drive cycle that includes several minutes of idle, low-speed cruise, medium-speed cruise, and deceleration before all monitors can be performed. Technician B says all monitors can be performed in five minutes of fast idling. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 19

The MAP sensor used on a turbocharged engine is calibrated the same as a MAP sensor for a nonturbocharged engine.

Question 20

A misfiring spark plug can cause a false oxygen sensor reading.

Question 21

A camshaft position sensor provides the PCM with data needed to control _____.

A) fuel injector timing
B) variable valve timing
C) ignition coil timing (COP ignition)
D) all answers are correct

Question 22

Which of the following is NOT a type of mass airflow sensor?

A) Karmen-Vortex
B) vane type
C) hot wire
D) Hall effect

Question 23

Which of the following tools cannot be used to test an oxygen sensor?

A) digital voltmeter (DMM)
B) analog voltmeter
C) lab scope
D) scan tool

Question 24

A conventional oxygen sensor needs to be heated to ________ degrees Fahrenheit before it can produce a usable signal.

A) 500
B) 750
C) 1,000
D) 1,200

Question 25

Which of the following tools should not be used to test an actuator unless the technician is directed to do so by the manufacturer's service procedures?

A) scan tool
B) DMM
C) jumper wires
D) lab scope

Question 26

Which of the following is NOT an actuator?

A) PCV valve
B) fuel injector
C) canister purge solenoid
D) idle air control valve

Question 27

A throttle position sensor has ______.

A) a 5-volt reference input terminal
B) a 0- to-5-volt signal output terminal
C) a ground terminal
D) all answers are correct

Question 28

Two technicians are discussing IAT sensors (intake air temperature). Technician A says the IAT sensor is an integral part of the mass airflow sensor (MAF). Technician B says the IAT is a discrete sensor located in the intake air passages or air cleaner assembly. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 29

Oxygen sensors may become contaminated by ______.

A) coolant from blown head gaskets
B) use of RTV silicone sealant in the intake system
C) excessive oil consumption caused by worn rings.
D) all answers are correct

Question 30

Which of the following statements is NOT true?

A) A conventional oxygen sensor has a minimum voltage of 0.000 volts and a maximum voltage of 1.000 volt.
B) On a V-type engine, bank 1 is the side of the engine where cylinder #1 is located.
C) An oxygen sensor measures the difference between the amount of oxygen inside the exhaust and the outside air.
D) A conventional oxygen sensor receives a 5-volt reference voltage from the PCM.

Question 31

When the system is running rich, the oxygen content in the exhaust is ______.

A) high
B) low
C) both A and B
D) neither A nor B

Question 32

A technician is rebuilding an engine and notices that one tooth is missing from the crank sensor pulse ring. Technician A says the pulse ring is broken and will have to be replaced. Technician B says that missing tooth identifies when cylinder #1 is at TDC and that the missing tooth is normal. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 33

A technician connects a DMM with a MIN/MAX/AVG function to the output of an oxygen sensor. The engine is run at 2000 RPM for several minutes. During the test, the voltage toggles rapidly between 150 and 900 millivolts. At the end of the test, the MAX voltage was .967 V, the MIN voltage was .087 V, and the AVG voltage was .683 V. Technician A says the sensor is faulty and should be replaced. Technician B says there could be a vacuum leak that caused the sensor voltage to have a higher than normal average. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 34

The engine coolant temperature sensor helps to control all the following EXCEPT:

A) fuel pressure
B) open loop/closed loop operation
C) EGR opening
D) ignition timing

Question 35

Technician A tests an MAF sensor with a scan tool by watching for erratic changes in flow while the engine idles. Technician B checks an MAF sensor by tapping it lightly with the handle of a screwdriver while watching the waveform on a lab scope. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 36

A MAP sensor with a varying frequency output can be tested with a(n) ______.

A) voltmeter
B) ohmmeter
C) DMM with a duty cycle function
D) DMM with a frequency function

Question 37

Which of the following problems would NOT cause a oxygen sensor to appear bad?

A) leaking fuel injector
B) leaking intake manifold gasket
C) leaking EGR valve
D) leaking muffler to tailpipe gasket

Question 38

An accelerator pedal position sensor (APP) is used on vehicles equipped with ______.

A) electronic throttle control
B) cruise control
C) torque converter clutch (TCC)
D) all answers are correct

Question 39

Two technicians are discussing testing switch type sensors. Technician A uses an ohmmeter. Technician B uses a voltmeter. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 40

An air/fuel ratio sensor is different from an oxygen sensor in that ______.

A) the signal output is a varying current (amps)
B) as the mixture becomes leaner, its output signal increases
C) the output responds to minor changes in air/fuel mixture, not just rich/lean conditions
D) all answers are correct

Question 41

The ____________________ sensor measures changes in intake manifold pressure that result from changes in engine load and speed.

Question 42

What types of problems could be caused by a faulty engine coolant temperature sensor?

Question 43

Describe the driving procedure that will allow the OBD-II system to complete all monitors.

Question 44

The BARO sensor informs the PCM about changes in weather and ____________________.

Question 45

What is the cause of photochemical smog?

Question 46

Drivability problems that do not set a DTC are diagnosed by ____________________ strategy.

Question 47

Normal throttle position sensor signal voltage at closed throttle [idle] is ____________________ volt.

Question 48

What is the primary function of an onboard diagnostic [OBD] system?

Question 49

A typical upstream oxygen sensor should have a voltage that toggles between ____________________ volt (low) and ____________________ volt (high) when the system is working in closed loop.

Question 50

The hot wire in the mass airflow sensor is held at a constant ____________________ degrees Celsius.

Question 51

A bad sensor ground can allow ____________________ to interfere with the signals sent to the PCM, possibly causing drivability problems.

Question 52

The ____________________ sensor measures the amount of air in grams per second entering the engine.

Question 53

The ____________________ sensor tells the PCM that detonation is occurring in the cylinders.

Question 54

The ____________________ is the key sensor in the closed loop mode.

Question 55

The voltage drop between the PCM and the battery negative terminal should be ____________________ millivolts or less.

Question 56

What is a waveform library?

Question 57

The PCM supplies a ____________________volt reference voltage to the MAP sensor.

Question 58

The vehicle speed sensor is typically mounted on the ____________________.

Question 59

A steel feeler gauge and voltmeter is used to test a ____________________ sensor.

Question 60

____________________ are electromechanical devices that convert an electrical current into mechanical action.

Question 61

What is the OBD-II DLC and where is it located?

Question 62

What is an OBD-II drive cycle?

Question 63

How does the OBD-II catalytic converter efficiency monitor work?

Question 64

What is a closed loop system?

Question 65

What is a freeze-frame?