Question 1

In a GDI system the fuel injectors spray fuel directly into the combustion chamber and require higher fuel pressures under heavy load, typically as high as:
A) 150 PSI
B) 625 PSI
C) 2,140 PSI
D) 10,500 PSI

Accepted Answer

In a Gasoline Direct Injection (GDI) system, the fuel injectors spray fuel directly into the combustion chamber at high pressures, especially under heavy load. The pressure can reach as high as 2,140 PSI to ensure efficient fuel atomization and mixing with air for optimal combustion.

Question 2

Technician A says one advantage of a variable valve timing system is that it allows a higher-compression engine to burn a lower octane fuel while still being able to control the potential for detonation. Technician B says that most VVT systems use engine oil pressure to control them hydraulically. Who is correct?
A) Technician A only
B) Technician B only
C) Both technicians
D) Neither technician

Accepted Answer

Variable Valve Timing (VVT) systems do indeed allow for higher compression engines to use lower octane fuel by adjusting the timing of valve opening and closing to control detonation. Additionally, most VVT systems utilize engine oil pressure to operate hydraulically, making both Technician A and Technician B correct.

Question 3

All of the following are used to combat the potential for vapor lock to occur EXCEPT :
A) The addition of a fuel return line
B) The deletion of the fuel return line
C) The relocation of the fuel pump back to within the fuel tank
D) The use of higher pressures within the fuel management system

Accepted Answer

Vapor lock occurs when fuel changes from a liquid to a gas while still in the fuel delivery system, which can prevent the engine from running properly. A fuel return line (A) helps by circulating excess fuel back to the tank, keeping it cooler and reducing the chance of vapor lock. Relocating the fuel pump back to within the fuel tank (C) helps maintain cooler fuel temperatures and consistent pressure, reducing vapor lock risk. Using higher pressures within the fuel management system (D) can also prevent vapor formation. Therefore, the deletion of the fuel return line (B) would not combat vapor lock; it could actually increase the risk by removing a mechanism designed to help manage fuel temperature and pressure.

Question 4

Reid Vapor Pressure (RVP) is a unit of measurement used to measure a fuel's:
A) Alcohol content
B) Ability to atomize
C) Octane
D) Volatility

Accepted Answer

RVP measures the volatility of gasoline or other fuels, indicating how easily the fuel vaporizes at a given temperature. This is crucial for understanding how the fuel behaves under different environmental conditions.

Question 5

Technician A says that if a fuel supply line ruptures during an accident resulting in fuel pressure loss and engine stall, the PCM will shut down the fuel pump. Technician B says that the fuel pump is controlled by the ignition switch only and should always run whenever the ignition switch is in the "run" position. Who is correct?
A) Technician A only
B) Technician B only
C) Both technicians
D) Neither technician

Accepted Answer

Technician A is correct because modern vehicles are designed with safety systems that shut off the fuel pump in the event of a significant accident to prevent fuel leaks and potential fires. The Powertrain Control Module (PCM) can detect situations like a sudden loss of fuel pressure or engine stall and cut power to the fuel pump. Technician B is incorrect because, while the ignition switch does play a role in powering the fuel pump, it's not the only control mechanism; safety systems can override it to prevent fuel flow in certain situations.

Question 6

What level of tach reference information is required for the PCM to properly control a COP ignition system?
A) Level one information indicating that "a pair of cylinders`pistons is approaching TDC"
B) Level two information indicating "which pair of cylinders`pistons is approaching TDC"
C) Level three information indicating "which cylinder of the piston pair approaching TDC is on the compression stroke"
D) None of this information is required for the PCM to control a COP ignition system

Accepted Answer

The PCM needs level three information to determine which specific cylinder is on the compression stroke to properly control the Coil-On-Plug (COP) ignition system.

Question 7

With the engine running, how is the PCM programmed to pulse the fuel injectors in a sequential fuel injection (SFI/SMPI) system?
A) Pulse all injectors simultaneously once each crankshaft revolution
B) Pulse one half of the injectors simultaneously on each crankshaft revolution
C) Pulse the injectors in pairs
D) Pulse the injectors individually in the engine's firing order

Accepted Answer

In a Sequential Fuel Injection (SFI) or Sequential Multi-Port Injection (SMPI) system, the Powertrain Control Module (PCM) is programmed to pulse the fuel injectors individually in the engine's firing order. This allows for more precise fuel delivery and timing, improving engine efficiency and performance.

Question 8

What is the primary purpose for replacing 14-volt systems with 42-volt systems?
A) To eliminate the charging system
B) To make the vehicle's electrical systems safer to work on
C) To increase the KV that the ignition coil(s) can provide
D) To provide more total wattage than a 14-volt system can provide

Accepted Answer

The primary purpose of replacing 14-volt systems with 42-volt systems in vehicles is to provide more total wattage. This is necessary to accommodate the increasing electrical demands of modern vehicles, including advanced safety systems, infotainment, and electrically powered steering and braking systems. Higher voltage systems can deliver the same power with less current, which can reduce the size and weight of wiring and improve efficiency.

Question 9

The emission system that is designed to route ambient air into the exhaust manifold during cold engine warm up only is known as:
A) EGR
B) AIR
C) EVAP
D) PCV

Accepted Answer

The AIR (Air Injection Reactor) system is designed to inject fresh air into the exhaust manifold during cold engine warm-up, which helps in the more complete burning of exhaust gases.

Question 10

What level of tach reference information is required in order for the PCM to properly control a "Waste Spark" ignition system?
A) Level one information indicating that "a pair of cylinders`pistons is approaching TDC"
B) Level two information indicating "which pair of cylinders`pistons is approaching TDC"
C) Level three information indicating "which cylinder of the piston pair approaching TDC is on the compression stroke"
D) None of this information is required in order for the PCM to control a "Waste Spark" system

Accepted Answer

Level two information indicating "which pair of cylinders`pistons is approaching TDC" is required for the PCM to properly control a "Waste Spark" ignition system. This allows the system to know which pair of cylinders to fire, as each spark will ignite the fuel in the cylinder on its compression stroke and will not affect the cylinder on its exhaust stroke.

Question 11

With modern terminology, the acronym "DI" refers to which type of ignition system?
A) A distributor ignition system using only one ignition coil
B) A "Waste Spark" distributorless ignition system using one ignition coil for each pair of cylinders
C) A "Coil-On-Plug" distributorless ignition system using one ignition coil for each cylinder
D) Both B and C

Accepted Answer

The answer of With modern terminology, the acronym "DI" refers...

Question 12

Technician A says that on fuel injection systems, the fuel pump relay carries the high amperage current for the fuel pump. Technician B says that on fuel injection systems with a return line, the fuel pressure regulator is located after the fuel pump and before the fuel injectors. Who is correct?
A) Technician A only
B) Technician B only
C) Both technicians
D) Neither technician

Accepted Answer

Technician A is correct because the fuel pump relay is designed to control the high amperage current needed to operate the fuel pump. Technician B is incorrect because the fuel pressure regulator is typically located after the fuel injectors in systems with a return line, not before them. It regulates the pressure of the fuel being delivered to the injectors and sends excess fuel back to the tank via the return line.

Question 13

In an electronic return-less SMPI system, the PCM controls all of the following EXCEPT:
A) Intake manifold pressure
B) Fuel pump speed
C) Fuel rail pressure
D) Fuel pressure differential across the fuel injectors

Accepted Answer

The PCM (Powertrain Control Module) does not directly control intake manifold pressure; this is influenced by the engine's operation and controlled through other means such as the throttle body and intake manifold design. The PCM does control fuel pump speed, fuel rail pressure, and can influence the fuel pressure differential across the fuel injectors in an electronic return-less Sequential Multi-Port Injection (SMPI) system.

Question 14

What level of tach reference information is required in order for the PCM to properly control a distributor ignition system?
A) Level one information indicating that "a pair" of cylinders' pistons are approaching TDC
B) Level two information indicating "which pair" of cylinders' pistons are approaching TDC
C) Level three information indicating which cylinder of the piston pair approaching TDC is on the compression stroke
D) None of this information is required in order for the PCM to control a distributor ignition system

Accepted Answer

The answer of What level of tach reference information is...

Question 15

During closed-loop operation of a fuel injection system, the PCM is programmed to perform all of the following functions EXCEPT :
A) controlling how much fuel is introduced into the intake manifold
B) fine-tuning the air-fuel ratio to minimize toxic emissions while maximizing fuel economy
C) retaining good driveability under cruise and light-to-moderate acceleration
D) maximizing driveability during cold starts and hard accelerations

Accepted Answer

During closed-loop operation, the primary focus of the PCM (Powertrain Control Module) is to maintain an optimal air-fuel ratio, especially under conditions of cruise and moderate acceleration, by adjusting the amount of fuel injected based on feedback from the oxygen sensor(s). This process aims to minimize emissions and maximize fuel economy while maintaining good driveability. However, maximizing driveability during cold starts and hard accelerations is more characteristic of open-loop operation, where the PCM relies on preset parameters rather than feedback from sensors, to ensure the engine runs rich enough for these conditions.

Question 16

What level of tach reference information is required in order for the PCM to properly control an SFI fuel management system?
A) Level one information indicating that "a pair of cylinders`pistons is approaching TDC"
B) Level two information indicating "which pair of cylinders`pistons is approaching TDC"
C) Level three information indicating "which cylinder of the piston pair approaching TDC is on the compression stroke"
D) None of this information is required in order for the PCM to control a SFI fuel management system.

Accepted Answer

Level three information is required for the PCM to properly control an SFI (Sequential Fuel Injection) system, as it needs to know which specific cylinder is on the compression stroke to time the fuel injection accurately.

Question 17

In order to ease cold weather starting, gasoline refiners produce gasoline in the winter months that has a:
A) Lower volatility
B) Higher volatility
C) Lower octane
D) Higher octane

Accepted Answer

In the winter months, gasoline refiners produce gasoline with higher volatility to ensure that it vaporizes more easily at lower temperatures, facilitating easier starting of engines in cold weather. Higher volatility means the gasoline will ignite more readily when the engine is cold.

Question 18

The emission control system that is designed to recirculate blow by gasses from the crankcase to the intake manifold is known as:
A) PCV
B) EGR
C) EVAP
D) AIR

Accepted Answer

The Positive Crankcase Ventilation (PCV) system is designed to recirculate blow-by gases from the crankcase to the intake manifold, reducing emissions by burning these gases as part of the combustion process.

Question 19

When battery voltage drops below a specified value, the PCM:
A) increases ignition dwell to compensate for a weakened ignition spark
B) enters open-loop operation
C) enriches the air-fuel mixture
D) Both A and C

Accepted Answer

When battery voltage drops below a specified value, the Powertrain Control Module (PCM) can increase ignition dwell to compensate for a weakened ignition spark and enrich the air-fuel mixture to ensure proper combustion under these conditions.

Question 20

A homogeneous charge compression ignition (HCCI) engine:
A) uses heat to auto-ignite the air-fuel charge
B) produces far less noise and vibration than a gasoline engine
C) creates more emissions than a gasoline engine
D) works most efficiently with a rich air-fuel ratio

Accepted Answer

HCCI engines use the heat of compression to auto-ignite the air-fuel mixture, similar to diesel engines, but with a homogeneous charge like gasoline engines.

Quiz 4: Common Operating Principles for Computerized Engine Control Systems

In a GDI system the fuel injectors spray fuel directly into the combustion chamber and require higher fuel pressures under heavy load, typically as high as:

All of the following are used to combat the potential for vapor lock to occur EXCEPT :

Reid Vapor Pressure (RVP) is a unit of measurement used to measure a fuel's:

What level of tach reference information is required for the PCM to properly control a COP ignition system?

With the engine running, how is the PCM programmed to pulse the fuel injectors in a sequential fuel injection (SFI/SMPI) system?

What is the primary purpose for replacing 14-volt systems with 42-volt systems?

The emission system that is designed to route ambient air into the exhaust manifold during cold engine warm up only is known as:

What level of tach reference information is required in order for the PCM to properly control a "Waste Spark" ignition system?

With modern terminology, the acronym "DI" refers to which type of ignition system?

Technician A says that on fuel injection systems, the fuel pump relay carries the high amperage current for the fuel pump. Technician B says that on fuel injection systems with a return line, the fuel pressure regulator is located after the fuel pump and before the fuel injectors. Who is correct?

In an electronic return-less SMPI system, the PCM controls all of the following EXCEPT:

What level of tach reference information is required in order for the PCM to properly control a distributor ignition system?

During closed-loop operation of a fuel injection system, the PCM is programmed to perform all of the following functions EXCEPT :

What level of tach reference information is required in order for the PCM to properly control an SFI fuel management system?

In order to ease cold weather starting, gasoline refiners produce gasoline in the winter months that has a:

The emission control system that is designed to recirculate blow by gasses from the crankcase to the intake manifold is known as:

When battery voltage drops below a specified value, the PCM:

A homogeneous charge compression ignition (HCCI) engine: