Deck 36: Multiplexing

Question 1

What early multiplexing technology was used to enable trailer ABS electronics to communicate with the tractor?

A) SAE J1939
B) CAN 2.0
C) PLC
D) EOM

Answer 1

PLC

Question 2

Which of the following is a correct interpretation of the acronym PLC when it is used in the context of trailer wiring?

A) power line carrier
B) protocol language communications
C) priority line communication
D) positive linear corollary

Answer 2

power line carrier

Question 3

Which of the following best defines baud rate when applied to data signaling?

A) Bandwidth
B) Number of fields
C) Symbol rate
D) Data volume

Answer 3

Symbol rate

Question 4

Which of the following terms best defines the speed limit on a telecommunications channel?

A) K-baud
B) Bandwidth
C) Frequency
D) Packet

Question 5

What critical data is contained in the arbitration field in a typical data packet?

A) priority status
B) receiver stations
C) message identifier
D) security encryption

Question 6

Technician A says that a data packet in a typical J1939 transaction consists of 7 fields. Technician B says that each field in a J1939 data packet has identical data volume. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 7

What colors are the twisted wire pair required to be in a J1939 data backbone?

A) blue and red
B) orange and black
C) yellow and blue
D) green and yellow

Question 8

Which of the following is true of the differential voltage used on a typical J1939 message packet?

A) must be 1 volt or less
B) usually 2.0 volts
C) usually 4.0 volts
D) equivalent to V-Bat voltage

Question 9

Technician A says that the reason for twisting the wires on a J1939 data backbone is to enable the data bus to act as a giant aerial. Technician B says that J1939 requires the data wire pair to cycle through one full cycle twist per 1 centimeter of length. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 10

Technician A says that truck electronic hardware specified to be J1939 compatible can be stub connected to a J1939 data bus without using transducer modules. Technician B says that multiplexing transducers and gateway modules enable communications between different chassis data buses using different protocols. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 11

Which of the following is used on a data bus backbone to minimize EMI (electromagnetic interference)?

A) gold plated connections
B) twisting data transmission wires
C) color coding the wires
D) grounding the data positive (+) wire

Question 12

Technician A says that OEMs permit some repairs to be made to low bus wiring. Technician B says that when a bus twisted wire pair is protected with foil, you can assume that it is categorized as low bus. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 13

Which of the following is NOT an advantage of a J1939 multiplexed chassis bus ?

A) reduces chassis hard wire volume
B) reduces input circuit hardware
C) improves inter-module communications
D) increases processor clock speeds

Question 14

Which field in a J1939 data packet is used to broadcast the size (data volume) of a message?

A) Ack
B) Arbitration
C) Control
D) Data

Question 15

Technician A says that the secret of effectively repairing a break in the twisted wire pair used in a J1939 data bus is to use plenty of solder in the repair joint to minimize resistance. Technician B says that a damaged Hi bus J1939 twisted wire pair should be replaced, rather than repaired. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 16

Technician A says that a J1939 Hi-bus twisted pair is usually shielded. Technician B says that the tin foil wrap found in some data buses provides a EMI protective shield. Who is right?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 17

How many resistors are contained in the ladder bridge of a 2-pole, Freightliner M2 smart switch?

A) 2
B) 5
C) 12
D) 72

Question 18

What does the processor that receives data from ladder switches use to determine switch status?

A) library of resistor values
B) ammeter
C) milli-voltmeter
D) protocol decoder

Question 19

Which of the following is another way of saying algorithm?

A) algebra
B) boot-up
C) mapping
D) inputs

Question 20

Technician A says that commercial vehicles today are required to use multiple TPS to signal multiple controllers connected on the powertrain bus. Technician B says that TPS status is broadcast on the data bus to be picked up by any controller with a SA on the bus that may require the signal. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 21

Which of the following is a major advantage of using an FET as a switch relay over a conventional relay?

A) resistance is so high, almost no current flows
B) FET resistance is low
C) almost no voltage is required to switch the pole status
D) FET are low cost option

Question 22

Technician A says that ladder switches can perform as a toggle switch. Technician B says that some smart switches are multi-function. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 23

Technician A says that the bus topology used in CAN 2.0/ J1939 ensures that no single module networked to the bus has more importance than any other. Technician B says that it is almost impossible to add controllers (SAs) to a J1939 data bus after it has been manufactured. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 24

What is the advantage of using FETs as relays in multiplexed truck chassis?

A) they can be switched with small currents
B) fast response to control gate signals
C) they are inexpensive
D) all of the above

Question 25

When an FET output permits excessive current flow on a multiplexed chassis, what circuit protection device opens the circuit?

A) virtual fuse
B) hard wire fuse
C) SAE #1 breaker
D) SAE #2 breaker

Question 26

What is the usual voltage differential of a J1939 message stop bit?

A) 1 volt
B) 2 volts
C) 3 volts
D) 5 volts

Question 27

When a voltage of value of 12 volts is measured off the CAN high line of a properly functioning J1939 data backbone, what is happening?

A) bus wake-up
B) message packet stop bit
C) ack field alert
D) dead short to insulated circuit

Question 28

What is the usual low bit voltage on a J1939 data transaction?

A) 1 volt
B) 2 volts
C) 3 volts
D) 5 volts

Question 29

Which of the following is known as the dominant bit in a J1939 multiplexing transaction?

A) the foil shield
B) low bit voltage
C) high bit voltage
D) V-Ref line

Question 30

Technician A says that any J1939 data bus can be accessed by connecting through a green 9-pin Deutsch connector. Technician B says that a J1939 data bus backbone can be accessed through a 3-pin Deutsch connector. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 31

Technician A says that the contents of any data bus message packet can be interpreted using a high frequency scopemeter. Technician B says that a scopemeter can be used to identify bus node activity ... or lack of activity. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 32

When a J1939 bus experiences a dead short to the power side of the circuit, what is the likely outcome?

A) shuts down the node closest to the short
B) no impact on bus communications
C) messages transmit with increased noise
D) shuts down all bus communications

Question 33

When a J1939 bus shorts to the ground side of the circuit, what is the likely outcome?

A) shuts down the node closest to the short
B) no impact on bus communications
C) messages transmit with increased noise
D) shuts down all bus communications

Question 34

Technician A says that J1939 node activity can be identified using a DMM set on V-DC min-max mode. Technician B says that the V-DC min-max readings taken while verifying J1939 bus activity should run between a low of 1 volt and a high of 5 volts. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 35

If a voltmeter is connected between J1939 CAN-low (positive test lead) and ground (negative test lead), what is the lowest measurement you would read if the data bus is functioning properly?

A) 0 volts
B) 1 volt
C) 3 volts
D) 5 volts

Question 36

Technician A says that a green 9-pin J1939 DLC must be used to connect to a post-2014 truck powertrain data bus. Technician B says that the black 9-pin J1939 DLC cannot connect to a post-2104 data bus. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 37

What could result if an EST that is not auto-bus detect capable (ABDC) is connected to a post-2014 J1939 data bus??

A) ?ECM failure
B) ?Multiple ECU failures
C) ?PDM failure
D) ?Complete bus shutdown

Question 38

?What prevents a black 9-pin J1939 DLC from connecting to a green 9-pin J1939 receptacle?

A) ?A blocking tang is used in the black connector.
B) ?The receptacle C-cavity socket is enlarged.
C) ?The receptacle F-cavity socket is reduced size.
D) ?A warning label is used on the green receptacle.

Question 39

When you have to work with multiple OEM chassis data bus systems, which type of communication adapter (CA) is recommended??

A) ?Any RP 1210 compatible CA
B) ?A generic RP 1210 CA
C) ?A chassis OEM RP 1210 CA
D) ?A blue RP 1210A CA

Question 40

When troubleshooting a J1939 bus, what has occurred if a suspect parameter group (SPG) is assigned to a component??

A) ?The component has failed
B) ?The ECM has failed
C) ?The ECU has failed
D) ?The component is reporting an abnormal condition circuit

Question 41

Technician A says that a green 9-pin J1939 DLC must be used to connect to a post-2014 Volvo truck J1939 data bus. Technician B says that the green 9-pin J1939 DLC is backward compatible and can connect to any pre-2014 black receptacle. Who is correct??

A) ?Technician A only
B) ?Technician B only
C) ?Both A and B
D) ?Neither A nor B

Question 42

When a global PGN message is broadcast on J1939, which of the following is true??

A) ?It can be received by any controller with a SA.
B) ?It targets a specific controller on the bus.
C) ?The bus is about to shut down
D) ?Bus communications are about to cease