Navigation System - Diagnostics: Description

The radio wave bands used in radio broadcasting are as follows:

Fig 1: Identifying Radio Band Frequencies & Types

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1. There are great differences in the size of the service area for AM and FM broadcasting. Sometimes FM stereo broadcast cannot be received even through AM can be received very clearly.

   Not only does FM stereo have the smallest service area, but it also picks up static and other types of interference ("noise") easily.

   Fig 2: Identifying Frequency Service Ranges

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1. Fading

   Besides electrical interference, AM broadcasts are also susceptible to other types of interference, especially at night. This is because AM radio waves bounce off the ionosphere at night. These radio waves then interfere with the signals from the same transmitter that reach the vehicle's antenna directly. This type of interference is called "fading".

   Fig 3: Identifying Cause Of Fading

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2. Multipath

   Interference caused by reflection of radio waves against obstructions is called "Multipath". Multipath occurs when radio signals emitted from the broadcast transmitter antenna are reflected against tall buildings or mountains and interfere with other signals which is to be received directly.

   Fig 4: Identifying Cause Of Multipathing

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3. Fade Out

   Because of the frequency higher than that of AM, FM radio wave tends to be reflected against obstructions such as tall buildings or mountains. For this reason, FM signals often seems to gradually disappear or fade away as the vehicle goes behind those obstructions. This phenomenon is called "fade out".

   Fig 5: Identifying Cause Of Fade Out

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1. It is very important to understand a customer's claim clearly in the noise troubleshooting. Use the following table to diagnose the phenomenon.
   Fig 6: Identifying Radio Wave Interference Conditions & Probable Causes

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   NOTE:

   If the condition where the noise occurs does not meet any of the above, find out the cause based on "Reception Problems". Refer to the description about Multipath and Fading mentioned previously.

NOTE: Never attempt to disassemble or oil any part of the player unit. Do not insert any object other than a disc into the magazine.
CD players use an invisible laser beam which could cause hazardous radiation exposure. Be sure to operate the player correctly as instructed.
1. Compact Disc (hereafter called "CD") Players use a laser beam pick-up to read the digital signals recorded on the CD and reproduce analog signals of the music, etc. There are 4.7 in. (12 cm) and 3.2 in. (8 cm) discs available for the CD player.

If the disc gets dirty, clean the disc by wiping the surface from the center to outside in the radial directions with a soft cloth.

Fig 7: Identifying Proper Disc Cleaning Procedure

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1. Components in the audio system communicate with each other through LAN. (Radio receiver with CD changer control function)
2. The master component of LAN is the navigation receiver assy with a resistance, which is necessary for communication.
3. When short circuit or circuit breakdown occurs in the LAN circuit, the audio system does not operate normally due to the communication cutoff.

1. The audio system has diagnosis function. (The diagnosis result is displayed on the CRT display of the radio receiver assy)
2. The component code (physical address), or three-digit number (in hexadecimal) is set for each component comprising LAN.
3. The logical address, or two-digit number (in hexadecimal) is set for each function and component unit in each component.