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HET2 > 204A - Electronic Fuel System Fundamentals > Flashcards

204A - Electronic Fuel System Fundamentals Flashcards

1
Q

What are some of the advantages of electronically controlled fuel injection systems?

A
  • Optimized engine performance
  • Lower exhaust emissions
  • Reduced fuel consumption
  • Less noise
  • Improved starting

204a pg. 1

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2
Q

A _______ is an output device that receives electrical signals from the ECM and converts them to a particular action.

A

Actuator.
Solenoids, torque motors, warning lights, fuel injectors.

204a pg. 2

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3
Q

What electronic waveform has a continually changing amplitude?

A

Analog signal. Either DC or AC voltage.

204a pg. 2

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4
Q

What electrical signal is characterized by a switching continuous amplitude level?

A

Digital signal.

204a pg. 3

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5
Q

What is a pulse width modulation signal?

A

A digital signal that pulses on and off with varying width (length of on time vs. length of off time).

204a pg. 3

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6
Q

What are electrical input devices that monitor pressures, temperatures, fluid levels, or mechanical movements?

A

Sensors / Transducers

204a pg. 4

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7
Q

Are ECM input sensors considered passive or active devices?

A

Passive.

204a pg. 7

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8
Q

Are ECM output devices considered passive or active?

A

Active

204a pg. 9

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9
Q

Most sensors produce an ______ signal that must be converted to a ______ signal for the CPU to process.

A

Analog signal that must be converted to a digital signal.

204a pg. 7

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10
Q

What does an ECM use to provide a stable reference voltage for sensor operation?

A

Voltage regulator or power supply.

204a pg. 7

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11
Q

Is RAM volatile or non-volatile memory?

A

Volatile. Memory is erased when power is removed.

204a pg. 9

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12
Q

What type of electronic memory do most current electronic controlled fuel injector systems use?

A

EEPROM

204a pg. 9

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13
Q

What type of memory would be used to store historical fault codes that are retained if power is lost?

A

EEPROM

204a pg. 9

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14
Q

Fuel injectors, solenoids, fan clutch, relays, brake control relays, and starting aids, are examples of what ECM output device?

A

Actuators

204a pg. 9

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15
Q

What is multiplexing?

A

The data link between electronic control modules that allows them to communicate with each other.

204a pg. 10

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16
Q

How many twists should be in a multiplexing data link wire pair?

A

12 twists per foot

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17
Q

What is baud rate?

A

Data transfer speed
Old system (J1587 & J1708): Less than 10 kbps
New system (CAN2.0/J1939): Exceeds 250 kbps

204a pg. 10

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18
Q

What is a network backbone?

A

The method of connection. Wires, twisted pair, fibre optic, etc.

204a pg. 10

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19
Q

What is network protocol?

A

The language for data communication.

204a pg. 10

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20
Q

The older networking protocols J1587 & J1708 had slower speeds of how many kbps?

A

Less than 10kbps

204a pg. 11

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21
Q

The newer networking protocol CAN 2.0 / J1939 use a data transfer speed of ______

A

Exceeding 250 Kbps

204a pg. 11

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22
Q

Why are appropriate network speeds important in modern equipment?

A

To meet the “real time” needs of current electronic engine controls.

204a pg. 11

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23
Q

Older multiplexing networks were connected in _______. The whole network would become non-functional if _____.

A

Connected in series. The whole network would become non-functional if one part of the network failed.

204a pg. 11

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24
Q

The newer CAN 2.0 protocol has modules connected in ______.

A

A linear or single track arrangement. If one module fails, the rest of the network remains functional.

204a pg. 12

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25
Q

How do modules on a multiplexing network know what transmissions to receive?

A

Each transmission includes an identifier and a priority level so each module only accepts the message it is programmed to receive.

204a pg. 12

26
Q

A negative temperature coefficient sensor will have ______ resistance when cold and a _______ resistance when hot.

A

High resistance when cold.
Low resistance when hot.

204a pg. 13

27
Q

A thermistor (temperature sensor) has how many wires?

A

Two.
5V reference and sensor return/Ground

204a pg. 13

28
Q

An ECM uses a current limiting resistor alongside a thermistor for what two reasons?

A
  • Provides an initial voltage drop for operation of the sensor circuit
  • Prevent excess current flow if the circuit shorts to ground

204a pg. 13

29
Q

With a two wire temperature sensor, what does the ECM measure?

A

Sensors provides a DC Analog signal.
ECM measures the voltage drop between the sensor signal and ground.

204a pg. 14

30
Q

What are the three wires in a pressure sensor?

A
  • 5V reference
  • Signal output
  • Ground

204a pg. 14

31
Q

What type of signal does an ECM measure from a three-wire pressure sensor?

A

DC analog signal.
(Not a voltage drop)

204a pg. 15

32
Q

What type of sensors are commonly used to provide the ECM with engine rpm and vehicle speed?

A

Reluctance type speed sensor

204a pg. 15

33
Q

With a reluctance type speed sensor, what happens to the generated AC output and frequency as the speed increases?

A
  • AC voltage increases
  • Frequency increases

204a pg. 16

34
Q

With a reluctance type speed sensor, what would happen to the generated output and frequency if the air gap between tone ring and sensor increased?

A
  • AC voltage would decrease
  • Frequency would remain the same
35
Q

Why might a speed sensor have four wires instead of two?

A

Some have a second coil in the sensor to serve as a backup signal.

204a pg. 16

36
Q

How does a sensor used to measure water in diesel function?

A

Sensor is supplied with a reference voltage. Water and diesel form a conductive path between two contacts which is interpreted by the ECM to determine water concentration.

204a pg. 17

37
Q

How many wires would there typically be on a fluid level sensor?

38
Q

What is the most common type of throttle position sensor?

A

Potentiometer

204a pg. 18

39
Q

How would a throttle position sensor be tested?

A
  • Back-probe the live circuit for voltages (5V reference, signal, GND)
  • Disconnect from the circuit and test resistances between the three terminals

204a pg. 18

40
Q

Warning and shutdown systems have what three basic functions?

A
  • Warn the operator of malfunctions
  • De-rate or shutdown the engine when damaging conditions exist
  • Generate fault codes

204a pg. 19

41
Q

With a sensor circuit malfunction, the ECM would most likely illuminate what operator warning light?

A

Yellow Check Engine light

204a pg. 20

42
Q

With a critical engine pressure or temperature malfunction, the ECM would most likely illuminate what operator warning light?

A

Red Stop Engine light

204a pg. 20

43
Q

Engine manufacturer codes can be separated into what two sections?

A
  • Engine protection codes
  • System fault detection codes

204a pg. 22

44
Q

What are some examples of engine protection codes?

A

Faults that will cause engine damage or failure.
- Low oil pressure
- High oil temperatures
- Low oil level
- Low oil coolant level
- High inlet air temperature

204a pg. 22

45
Q

What are some examples of system fault detection codes?

A

Faults occurring with the control system. Short circuits, ground faults, opens, etc.
- Coolant temp sensor circuit high voltage
- Oil pressure sensor circuit low voltage
- Battery voltage low
- Missing engine speed signal
- Injector output circuit open

204a pg. 22

46
Q

What is the difference between an engine protection code and system fault detection code?

A

Engine Protection Codes: Faults that will cause engine damage or failure

System Fault Detection Codes: Faults with the control system - wiring, sensors, actuators

204a pg. 22

47
Q

Electronic control modules generate diagnostic trouble codes based on what two sources of information?

A
  • Information from sensor circuits
  • Set values programmed into the ECM

204a pg. 23

48
Q

What is usually the cause of many of the problems in electronically controlled fuel injection systems?

A

The connecting devices - wiring harnesses & connectors - linking the solid state components together.

204a pg. 25

49
Q

If a two-wire temperature sensor has a short, what code would the ECM display?

A

Voltage low

204a pg. 25

50
Q

If a temperature sensor had an electrical open, what signal would the ECM see?

A

A voltage drop of 5V (reference voltage).
Sensor circuit voltage High.

204a pg. 26

51
Q

Where is the Diagnostic Data Link (DDL) often mounted?

A
  • Cab-mounted to protect connector from dirt, water, corrosion.
  • On the engine for stationary engines.

204a pg. 28

52
Q

How many pins does the J1587 & J1708 DDL connector have?

A

Six pins.
For the older protocol with slower speeds of 10kbps.

204a pg. 29

53
Q

How many pins does the J1939 DDL connector have?

A

Nine pins.
For the newer protocol with speeds exceeding 250kbps.

204a pg. 29

54
Q

To minimize damage to the ECM, what should be done when connecting and disconnecting from the data link port?

A

Vehicle key switched off

204a pg. 32

55
Q

Customer and Manufacturer programmable features are stored in what type of ECM memory?

A

EEPROM

204a pg. 35

56
Q

What are some examples of customer programmable features in an ECM?

A
  • Cruise control options
  • Vehicle speed limiting
  • Progressive shifting
  • Gear down protections
  • PTO speed settings
  • Engine brake options
  • Low idle speed adjustments
  • Idle shutdown timer

204a pg. 35

57
Q

What are some examples of manufacturer programmable features in an ECM?

A
  • Software upgrades
  • Engine rating

204a pg. 35

58
Q

Cruise control speed settings are based on the frequency of the signal received from the vehicle speed sensor. This frequency is controlled by what four factors?

A
  • Rear axle ratio
  • Tire revolutions per mile
  • Number of teeth on transmission output shaft tone ring
  • Top gear ratio of transmission

204a pg. 37

59
Q

True or False.
Vehicle speed sensors and engine rpm sensors provide a variable frequency signal to the ECM.

A

True.

204a pg. 16

60
Q

A typical throttle position sensor uses a potentiometer to provide the ECM with a variable DC voltage signal that varies between what two levels?

A

0.5V at idle to 4.5V at full throttle

HET2 (29 decks)

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