Question 1

The air/fuel ratio sensor produces a voltage output relative to:
A) the air-fuel mixture in the cylinders
B) the intake air temperature
C) both A and B
D) the oxygen content of the exhaust stream

Accepted Answer

D

Question 2

Mass air flow sensor voltage corresponds to:
A) engine load and crankshaft speed
B) throttle opening and engine load
C) engine and vehicle speed
D) engine load and camshaft speed

Accepted Answer

The mass air flow sensor measures the amount of air entering the engine, which directly correlates to the throttle opening (how much the driver is pressing the accelerator) and the engine load (how much power the engine needs to produce). This information is crucial for the engine control unit (ECU) to calculate and deliver the correct fuel mixture for optimal combustion.

Question 3

Since the early 2000s, the wide-range air-fuel ratio sensor (AFS) has replaced the conventional zirconia oxygen sensor.

Accepted Answer

The wide-range air-fuel ratio sensor (AFS), also known as a wideband oxygen sensor, has largely replaced the conventional zirconia oxygen sensor in many applications since the early 2000s due to its ability to provide more precise measurements of the oxygen content in the exhaust gas over a wider range of air-fuel ratios. This allows for better control of the engine's air-fuel mixture, improving efficiency and reducing emissions.

Question 4

Technician A says that in a fuel injection system, the MAF sensors may be vane-type, heated grid-type, or hot wire-type. Technician B says that the PCM supplies a richer air-fuel ratio when it gets a signal that current flow is increasing to maintain temperature in the MAF module. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Both technicians are correct. Technician A is correct in stating that MAF (Mass Air Flow) sensors can be of different types, including vane-type, heated grid-type, or hot wire-type. Technician B is correct in stating that the PCM (Powertrain Control Module) enriches the air-fuel mixture in response to increased current flow in the MAF sensor to maintain its temperature, which is a characteristic of how hot wire MAF sensors function.

Question 5

The OBD II test strategies compare sensor inputs to one another during a rationality test to see if the inputs make sense with the expected outcome .

Accepted Answer

OBD II (On-Board Diagnostics II) systems perform rationality tests by comparing inputs from various sensors to ensure they make sense together and match expected outcomes, helping to identify malfunctions or inefficiencies in the vehicle's operation.

Question 6

The coolant temperature sensor is a negative temperature coefficient sensor; therefore:
A) as temperature increases, resistance increases
B) as temperature increases, the amplitude of the sine wave increases
C) as temperature increases, resistance decreases
D) as temperature decreases, the amplitude of the sine wave increases

Accepted Answer

A negative temperature coefficient sensor decreases in resistance as the temperature increases.

Question 7

A twisted pair of wires helps to eliminate the induction of electro-magnetic-interference (EMF).

Accepted Answer

Twisting the wires together helps to cancel out electromagnetic interference (EMI) from external sources because the loop area between the wires (which is susceptible to interference) is minimized, and any interference that does get induced into the wires tends to be canceled out since it affects both wires equally but in opposite phases.

Question 8

Technician A says that when the voltage output of an air/fuel ratio sensor shifts below 3.3 V, it indicates a rich air/fuel mixture ratio. Technician B says that when the voltage output of an air/fuel ratio sensor shifts below 3.3 V, it indicates a lean air/fuel mixture ratio. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

When the voltage output of an air/fuel ratio sensor shifts below 3.3 V, it indicates a rich air/fuel mixture ratio.

Question 9

Prior to OBD II, many automotive PCMs used an unalterable programmable read-only memory (PROM).

Accepted Answer

Before the standardization of On-Board Diagnostics II (OBD II), many automotive Powertrain Control Modules (PCMs) utilized a PROM (Programmable Read-Only Memory) chip that was programmed during manufacturing and could not be altered or reprogrammed after it left the factory. This meant that any updates or changes to the vehicle's software required physical replacement of the PROM chip.

Question 10

OBD II can store information about adjustments the PCM has made for component wear and varied operating conditions. The ability of OBD II to adjust calibrations to compensate for these defects and less-than-ideal conditions is known as:
A) compensatory regulation
B) modification component
C) adaptive strategy
D) adjustment capacity

Accepted Answer

OBD II's adaptive strategy allows the Powertrain Control Module (PCM) to adjust its calibrations to compensate for component wear and varied operating conditions, ensuring optimal performance despite changes or defects.

Question 11

The air-fuel ratio sensor (AFS) has the ability to measure air-fuel ratios from as lean as 35:1 to as rich as 11:1.

Accepted Answer

The air-fuel ratio sensor (AFS), also known as a wideband oxygen sensor, is designed to provide feedback to the engine control unit (ECU) over a wide range of air-fuel ratios, allowing it to accurately measure very lean mixtures around 35:1 to very rich mixtures around 11:1, unlike traditional oxygen sensors which are limited to a narrow band around the stoichiometric point of 14.7:1.

Question 12

Physically, the air/fuel ratio sensor looks very similar to a conventional oxygen sensor from the outside.

Accepted Answer

Both the air/fuel ratio sensor and the conventional oxygen sensor have similar external appearances, typically featuring a threaded body that screws into the exhaust system, a connector for wiring, and a protective shield. However, they function differently and are designed for different purposes in engine management systems.

Question 13

The air/fuel ratio sensor (AFS) circuit can be measured directly with a digital multimeter with accuracy.

Accepted Answer

The air/fuel ratio sensor (AFS) generates a voltage or current signal that varies with the oxygen content in the exhaust, and it operates at a higher temperature than traditional oxygen sensors. Directly measuring its circuit with a digital multimeter may not provide accurate information about its functionality due to the sensor's complex operation, which involves specific voltage or current changes in response to oxygen levels. Testing typically requires specialized diagnostic tools that can interpret the sensor's output signals under operating conditions.

Question 14

Technician A says that when a DTC is cleared from the PCM memory, the system readiness monitors are also cleared. Technician B says that after an emissions repair is completed, the DTCs stored should be cleared from the PCM. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Both technicians are correct. When a Diagnostic Trouble Code (DTC) is cleared from the Powertrain Control Module (PCM) memory, the system readiness monitors are reset, which is what Technician A states. Technician B is correct in saying that after an emissions repair is completed, the stored DTCs should be cleared from the PCM to reset the system and start fresh with monitoring for any further issues.

Question 15

Technician A says that a digital voltage signal is continuously variable within a certain voltage range. Technician B says an amplification circuit in the input conditioning chip will amplify a low voltage signal. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Technician B is correct because an amplification circuit in the input conditioning chip is indeed used to amplify low voltage signals, making them more detectable or usable by the system. Technician A is incorrect because a digital voltage signal is not continuously variable within a certain voltage range; instead, it switches between discrete values, typically representing binary 0s and 1s.

Question 16

Most of today's computers utilize a technology that allows for electronically erasable programmable read-only memory (EEPROM).

Accepted Answer

EEPROM technology is widely used in today's computers and electronic devices, allowing data to be electronically erased and reprogrammed.

Question 17

A serial data stream is an analog code that is known as a binary code.

Accepted Answer

A serial data stream is a digital code that represents data in a series of binary bits (0s and 1s), not an analog code.

Question 18

An air/fuel ratio sensor is used instead of a conventional oxygen sensor because:
A) the air/fuel ratio sensor does not require a heater element
B) an air/fuel ratio sensor allows for more accurate fuel control
C) an air/fuel ratio sensor is less expensive than a conventional oxygen sensor
D) none of the above

Accepted Answer

An air/fuel ratio sensor provides more precise data on the oxygen content in the exhaust, allowing the engine control unit (ECU) to adjust the fuel mixture more accurately for optimal combustion, emissions, and fuel economy. Unlike conventional oxygen sensors, which only indicate if the mixture is rich or lean, air/fuel ratio sensors can measure the exact ratio, enabling finer control.

Question 19

The AFS operating temperature is 750°F (400°C), which is substantially colder than the conventional oxygen sensor operational temperature of 1200°F (650°C).

Accepted Answer

The answer of The AFS operating temperature is 750°F (400°C),...

Question 20

Technician A says that the conventional oxygen sensor produces a fluctuating high/low voltage signal. Technician B says an air/fuel ratio sensor produces a more constant output signal voltage. Who is correct?
A) A only
B) B only
C) both A and B
D) neither A nor B

Accepted Answer

Technician A is correct because conventional oxygen sensors do indeed produce a fluctuating high/low voltage signal, indicating whether the exhaust is rich (high voltage) or lean (low voltage). Technician B is also correct because an air/fuel ratio sensor, also known as a wideband oxygen sensor, produces a more constant and precise output signal voltage that allows the engine control unit to closely monitor and adjust the air/fuel mixture for optimal performance and emissions.

Quiz 5: Computers and Input Sensors

The air/fuel ratio sensor produces a voltage output relative to:

Mass air flow sensor voltage corresponds to:

Since the early 2000s, the wide-range air-fuel ratio sensor (AFS) has replaced the conventional zirconia oxygen sensor.

Technician A says that in a fuel injection system, the MAF sensors may be vane-type, heated grid-type, or hot wire-type. Technician B says that the PCM supplies a richer air-fuel ratio when it gets a signal that current flow is increasing to maintain temperature in the MAF module. Who is correct?

The OBD II test strategies compare sensor inputs to one another during a rationality test to see if the inputs make sense with the expected outcome .

The coolant temperature sensor is a negative temperature coefficient sensor; therefore:

A twisted pair of wires helps to eliminate the induction of electro-magnetic-interference (EMF).

Technician A says that when the voltage output of an air/fuel ratio sensor shifts below 3.3 V, it indicates a rich air/fuel mixture ratio. Technician B says that when the voltage output of an air/fuel ratio sensor shifts below 3.3 V, it indicates a lean air/fuel mixture ratio. Who is correct?

Prior to OBD II, many automotive PCMs used an unalterable programmable read-only memory (PROM).

OBD II can store information about adjustments the PCM has made for component wear and varied operating conditions. The ability of OBD II to adjust calibrations to compensate for these defects and less-than-ideal conditions is known as:

The air-fuel ratio sensor (AFS) has the ability to measure air-fuel ratios from as lean as 35:1 to as rich as 11:1.

Physically, the air/fuel ratio sensor looks very similar to a conventional oxygen sensor from the outside.

The air/fuel ratio sensor (AFS) circuit can be measured directly with a digital multimeter with accuracy.

Technician A says that when a DTC is cleared from the PCM memory, the system readiness monitors are also cleared. Technician B says that after an emissions repair is completed, the DTCs stored should be cleared from the PCM. Who is correct?

Technician A says that a digital voltage signal is continuously variable within a certain voltage range. Technician B says an amplification circuit in the input conditioning chip will amplify a low voltage signal. Who is correct?

Most of today's computers utilize a technology that allows for electronically erasable programmable read-only memory (EEPROM).

A serial data stream is an analog code that is known as a binary code.

An air/fuel ratio sensor is used instead of a conventional oxygen sensor because:

The AFS operating temperature is 750°F (400°C), which is substantially colder than the conventional oxygen sensor operational temperature of 1200°F (650°C).

Technician A says that the conventional oxygen sensor produces a fluctuating high/low voltage signal. Technician B says an air/fuel ratio sensor produces a more constant output signal voltage. Who is correct?