Electrical Fundamentals - B

Question 1

What must be done with malfunctioning audible warning devices?

Answer 1

Replaced

Question 2

When multiple warning lights uses same buzzer, how is it wired?

Answer 2

In parallel to lights with a isolating diode to prevent the other lights from activating.

Question 3

The warning light control device may control what?

Answer 3

Either the lights battery voltage supply circuit or the lights ground circuit

Question 4

Instrument and gauges

Answer 4

Also called meters, can be either direct or indirect

Question 5

Direct acting gauges

Answer 5

Do not use sending units. The gauge is connected directly to source of what they are measuring.

Question 6

Indirect acting gauges

Answer 6

Require sending units and can receive analog or digital signals

Question 7

Analog gauge

Answer 7

Is a electromechanical device with needles or pointers that swing across a calibrated scale.

Question 8

What are the 3 most common types of analog gauges

Answer 8

Balancing coil
Stepper motor
Air core

Question 9

Directly proportional gauge

Answer 9

As resistance increases, level on gauge increases

Question 10

Indirectly proportional gauge

Answer 10

As resistance increases, level on gauge decreases

Question 11

Thermistor

Answer 11

A variable resistor whose resistance changes significantly with changes in temperature.

Question 12

Digital ammeter

Answer 12

Uses a hall effect sensor and an integrated circuit amplifier (similar to amp clamp)

Question 13

Pulses per mile (PPM)

Answer 13

=M x Ra x N. Where M is tire rev’s per mile, Ra is rear axle ratio, and N is number of teeth on tone ring.

Question 14

How does a digital gauge receive its signal?

Answer 14

Over the vehicles data link

Question 15

A Hall effect sensor sends an amperage signal to the ammeter by:

Answer 15

Using a integrated circuit amplifier

Question 16

Baud rate

Answer 16

Is the speed of the data transfer over the network, commonly measured in kilobits per second (kb/s). One baud is the transfer of one digital signal, or bit per second

Question 17

The Backbone

Answer 17

In most vehicles is a twisted pair of wires that are often shielded with a copper wire to prevent electromagnetic interference (EMI). Is also referred to as the data bus

Question 18

Stub

Answer 18

Is a segment of data link that branches off the backbone and connects to each node. Can be up to 1 meter in length

Question 19

Node

Answer 19

Is a computer or other device that has a unique network address. Each ECM is considered a node on the data link

Question 20

Vehicle communication data bus

Answer 20

The communication network that connects to all of the multiplexed components of a vehicle system (J1708, J1939)

Question 21

Protocol

Answer 21

Is a common language for data communication between control modules. J1587 and CAN are the common protocols in heavy duty vehicles.

Question 22

(CAN) Controller Area Network

Answer 22

Is a communication protocol used in on-highway trucks. Provides a serial communications protocol, meaning that all of the information sent on the network is in sequence.

Question 23

Data Links

Answer 23

Provide for the transmission of input and output signals between nodes and diagnostic scan tools

Question 24

Multiplexing

Answer 24

Is the ability to send and receive digital electronic signals over a pair of wires (data link) at high speed

Question 25

What are the advantages of using a data link over point to point wires? (4)

Answer 25

Minimizes the amount of electrical wiring the vehicle uses. Provides an easy way to add electrically controlled components Reductions to size and cost of wiring harness Fewer wire and connectors means more reliability

Question 26

What is the most popular type of multiplexing?

Answer 26

Time division multiplexing

Question 27

The J1587/J1708 has what system limitations?

Answer 27

Number of nodes is limited to 20, communication speed is slow (9.6 kb/s), messages limited to maximum of 21 bytes (168 bits)

Question 28

J1587 MID

Answer 28

Message identifier, is 1 byte long and indicates the source of the address of the transmitting node. Each node may be assigned a number between 1 and 255, most common are 128-255

Question 29

J1587 PID

Answer 29

Parameter identifier, usually 1 byte long and indicates to what parameter the following data corresponds. Can be 0-255

Question 30

J1587 Parameter data bytes

Answer 30

All PID's must be followed by a least one data value. Can not exceed 18 bytes. PID 0-127 - 1 data byte PID 128-191 - 2 data byte PID 192-255 - 1 to 18 data byte

Question 31

J1587 Checksum

Answer 31

Follows the final byte of data. it is 1 byte long and completes the message

Question 32

J1587 bus

Answer 32

Is an unshielded twisted pair cable, usually orange and white in colour, does not require termination resistors

Question 33

What connector was standard between 1996 and 2001?

Answer 33

6 pin deutsch HD10-6-12P

Question 34

What connector did most OEMs convert to in 2001?

Answer 34

9 pin deutsch HD10-9-1939P

Question 35

J1939 PGN

Answer 35

Parameter group number, usually 8 bytes long and its purpose is to identify the message and its data

Question 36

J1939 SPN

Answer 36

Suspect parameter number 19 bits, is used to identify and report where the failure has occurred

Question 37

J1939 FMI

Answer 37

Failure mode identifier, 5 bits, identifies the type of failure

Question 38

What is the order of the fields in the Can message frame?

Answer 38

``` Arbitration - Identifies priority and sender Control - Additional info Data - Additional info CRC- Checks for errors ACK - acknowledges receipt End - terminates message ```

Question 39

J 1939 data bus cables

Answer 39

Yellow - the CAN high (+) Green - the CAN low (-) 1939-11 is shielded or heavy 1939-15 is unshielded or lite

Question 40

J1939 cable should have how many twists?

Answer 40

12 twists per foot

Question 41

What does the j1939 cable have on the ends of each wire?

Answer 41

A 120 ohm resistor

Question 42

Messages on the J1939 need to be terminated in order to minimize what?

Answer 42

Standing waves, which are when old messages are bounced into new messages corrupting the data in the new message.

Question 43

What happens when the terminating resistors fail?

Answer 43

If 1 fails is missing, communication glitches will occur. | If both are missing, communication will fail all together.

Question 44

What is the expected idle voltage on the J1587.

Answer 44

High - 3.2 - 3.9 VDC that is constantly changing | Low - 0.7 -2.0 VDC that is constantly changing

Question 45

What is the expected idle voltage on the J1939

Answer 45

2.0 - 4.0 VDC for both the High and Low

Question 46

What is the expected resistance when testing between CAN high/Can low and ground?

Answer 46

1 - 4 M ohms or OL

Question 47

What is the expected resistance between the J1939 shield wire and a chassis ground?

Answer 47

0 Ohms

Question 48

Control Logic

Answer 48

Is the ability to program certain features to automatically respond once certain conditions are met (EX. headlights automatically turn on when wipers are turned on)

Question 49

Bulkhead control module

Answer 49

BHM, known as the brains of the system, also known as the input module

Question 50

Chassis control module

Answer 50

CHM, also known as output module, works with the BHM to communicate input and output signals from the components connected to it.