Deck 22: Driver Information and Navigation Systems

Question 1

Two technicians are discussing a fuel gauge on a General Motors vehicle. Technician A says that if the ground wire connection to the fuel tank sending unit becomes rusty or corroded, the fuel gauge will read lower than normal. Technician B says that if the power lead to the fuel tank sending unit is disconnected from the tank unit and grounded (ignition on), the fuel gauge should go to empty. Which technician is correct?

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

Answer 1

A fuel gauge system is shown below:
Figure 1
A fuel tank unit has a float connected to the variable resistor. As the fuel level changes the resistance of the variable resistor also changes. As the resistance of the tank unit changes, the dash mount gauge also changes which is displayed to the driver.
If the tank sending unit is disconnected, then the operation will not occur and then the change in resistance will not be forwarded to the dash unit. Hence, the needle will always remain at empty only. The ground wire connection to the fuel tank will be able to conduct even after being rusty. Hence, technician B is correct and technician A is incorrect.
Thus, the correct option is
and options 'a', 'c' and 'd' are incorrect.

Question 2

How does a stepper motor analog dash gauge work?

Answer 2

A stepper motor is a type of motor which can rotate in small steps depending upon the input signal provided to it. Analog displays on the dash uses stepper motor to move the needle. A discreet signal is provided to the motor which controls the rotation of the steps. A stepper motor can have 120 steps of motion.
The position of the stepper motor's can be monitored by PCM. The position of the dial is relative of the number of the steps that are sent to the stepper motor, this relative position is maintained by the PCM.
A stepper motor with four wires is shown below:
Figure 1

Question 3

If an oil pressure warning lamp on a General Motors vehicle is on all the time, yet the engine oil pressure is normal, the problem could be a _______.

A) Defective (shorted) oil pressure sending unit (sensor)
B) Defective (open) oil pressure sending unit (sensor)
C) Wire shorted-to-ground between the sending unit (sensor) and the dash warning lamp
D) Both a and c

Answer 3

The oil pressure warning lamp is on only when the pressure of the oil is low, in any other case if it is on then there's a fault. Firstly, the oil tank should be manually checked if it is not low, then the possible situations are that either the oil pressure unit (sensor) is shorted by some means or the wire between the sending unit and the dash warning lamp has been shorted.
In any condition mentioned above, the warning light will stay on. Hence, both options 'a' and 'c' are correct.
Thus, the correct option is
.

Question 4

What are LED, LCD, VTF, and CRT dash displays? Describe each.

Question 5

How do you diagnose a problem with a red brake warning lamp?

Question 6

A brake warning lamp on the dash remains on whenever the ignition is on. If the wire to the pressure differential switch (usually a part of a combination valve or built into the master cylinder) is unplugged, the dash lamp goes out. Technician A says that this is an indication of a fault in the hydraulic brake system. Technician B says that the problem is probably due to a stuck parking brake cable switch. Which technician is correct?

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

Question 7

How do you test the dash unit of a fuel gauge?

Question 8

A customer complains that every time the lights are turned on in the vehicle, the dash display dims. What is the most probable explanation?

A) Normal behavior for LED dash displays
B) Normal behavior for VTF dash displays
C) Poor ground in lighting circuit causing a voltage drop to the dash lamps
D) Feedback problem most likely caused by a short-tovoltage between the headlights and dash display

Question 9

How does a navigation system determine the location of the vehicle?

Question 10

Technician A says that LCDs may be slow to work at low temperatures. Technician B says that an LCD dash display can be damaged if pressure is exerted on the front of the display during cleaning. Which technician is correct?

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

Question 11

Technician A says that backup sensors use LEDs to detect objects. Technician B says that a backup sensor will not work correctly if the paint is thicker than 0.006 in. Which technician is correct?

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

Question 12

Technician A says that metal-type tinting can affect the navigation system. Technician B says most navigation systems require a monthly payment for use of the GPS satellite. Which technician is correct?

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

Question 13

Technician A says that the data displayed on the dash can come from the engine computer. Technician B says that the entire dash assembly may have to be replaced even if just one unit fails. Which technician is correct?

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

Question 14

How does changing the size of the tires affect the speedometer reading?

A) A smaller diameter tire causes the speedometer to read faster than actual speed and more than actual mileage on the odometer.
B) A smaller diameter tire causes the speedometer to read slower than the actual speed and less than the actual mileage on the odometer.
C) A larger diameter tire causes the speedometer to read faster than the actual speed and more than the actual mileage on the odometer.
D) A larger diameter tire causes the speedometer to read slower than the actual speed and more than the actual mileage on the odometer.