Deck 12: Instrumentation

Question 1

Referring to the following figure, low air pressure switch 1 and switch 2 are connected in parallel.

Answer 1

True

Question 2

Referring to the figure shown below, switch 1 is normally open since low air brake system pressure is an abnormal condition.

Answer 2

False

Question 3

Referring to figure shown below, a blown fuse F5-C would prevent the low air lamp from illuminating.

Answer 3

False

Question 4

Referring to the following figure, the vehicle speed sensor would likely be connected directly to the instrument panel cluster.

Question 5

All of the current leaving the vehicle batteries would also flow through the instrument panel cluster ammeter gauge since the gauge is in series with the positive battery cable.

Question 6

A bimetallic gauge makes use of which of the following to cause the gauge needle to move:

A) Magnetism
B) Stepper motor
C) Bucking coil
D) Thermal expansion of dissimilar metals

Question 7

Technician A says that an inaccurate bimetallic gauge could be caused by a faulty instrument voltage regulator. Technician B says that an inaccurate bimetallic gauge could be caused by excessive resistance in the associated wiring harness. Who is correct?

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

Question 8

Referring to the following figure, what could cause the low air lamp to illuminate?

A) Switch 1 is closed.
B) Switch 2 is closed.
C) Shorted to ground circuit between the low air lamp and switch 1
D) All of the above could cause the low air lamp to illuminate.

Question 9

Referring to the figure shown below, technician A says that switch 1 and switch 2 provide a ground for the low air lamp when closed. Technician B says that switch 1 and switch 2 provide a ground for the speedometer/tachometer module to cause an alarm to sound. Who is correct?

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

Question 10

Referring to the following figure, technician A says that a loose connection at the left dash panel ground stud could prevent the low air lamp from illuminating and the audible alarm from sounding when air in the brake systems is low. Technician B says that an open circuit 11-GD could cause the low air lamp to illuminate. Who is correct?

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

Question 11

Referring to the figure shown below, an inoperative low air warning lamp in the instrument panel cluster with all other gauges and warning lamps working correctly would be most likely caused by which of the following?

A) Open circuit between the instrument panel cluster and the engine control module (ECM)
B) Loose connection at the left dash panel ground stud
C) Blown fuse F5-C
D) None of the above

Question 12

Referring to the following figure, an indication of low engine oil pressure could be caused by which of the following:

A) Low engine oil level
B) Excessive wear of internal engine components
C) Faulty engine oil pressure sensor
D) All of the above

Question 13

Referring to the figure shown below, an inoperative tachometer with no other complaints could be caused by which of the following?

A) Open data link circuit between instrument panel cluster and engine ECM
B) Defective engine crankshaft position sensor
C) Broken tachometer drive cable
D) None of the above

Question 14

Technician A says that it is OK to disconnect a suspected faulty brake pressure warning switch to get a truck back on the road provided the truck operator signs a waiver. Technician B says that a fuel level sending unit float that is filled with fuel would likely cause the fuel level gauge to indicate Full. Who is correct?

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

Question 15

Which of the following is a true statement?

A) The best way to test a gauge is to short the wire at the sending unit to +12V.
B) The output of a vehicle speed sensor is the vehicle speed.
C) A d'Arsonual type gauge would typically be used as an ammeter.
D) All of the above are true statements.

Question 16

Of the choices listed, which is the best method of troubleshooting an instrumentation problem?

A) Replace components starting with the sensor or sending unit until the instrumentation is working correctly.
B) Short the wiring at the associated sensor or sending unit to ground to determine if the wiring is OK.
C) Pierce the wire insulation at the sending unit with a test light to determine if voltage is present.
D) Use OEM-provided information and procedures to troubleshoot the cause of the instrumentation problem.

Question 17

Technician A says that it may be necessary to modify an engine ECM programmable parameter using an electronic service tool after changing the rear axle ratio. Technician B says that it may be necessary to modify DIP switch settings on the instrument panel cluster after changing the rear axle ratio. Who is correct?

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

Question 18

A work order indicates that the voltmeter gauge only indicates approximately 12V with the engine running. Which of these would be the first step of the troubleshooting process?

A) Replace the voltmeter gauge.
B) Test the charging system.
C) Verify the complaint.
D) Tighten the alternator drive belt.

Question 19

A fully multiplexed J1939 instrument panel cluster on a truck with a body control module has the following inoperative gauges: engine oil pressure, coolant temperature, tachometer, and speedometer. The automatic transmission oil temperature gauge, air pressure gauges, fuel level gauge, and turn signal indicators still function correctly. What could be a possible cause of the inoperative gauges?

A) Short circuit between CAN + and CAN -
B) CAN + is shorted to ground.
C) Missing terminating resistors
D) An open CAN + or CAN - circuit between the engine ECM and the instrument panel cluster

Question 20

After checking a truck for other problems after completing an unrelated repair, you notice that on a truck with ABS that the ABS warning lamp does not illuminate at any time, even when the ignition is first switched on. What should you do?

A) Nothing, the ABS system only illuminates the warning lamp if there is a problem with the ABS system.
B) Use a test light to pierce the applicable wire at the ABS ECU to check for 12V.
C) Ignore it; if the truck operator wanted it fixed he would have mentioned it.
D) Notify your service manager or service writer so that they can make the truck operator aware of the condition.