Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Section 600 (Audio System - Diagnosis): Description
- COMMUNICATION SYSTEM
- Components in the audio system communicate each other though AVC-LAN. (Radio receiver with CD changer control function)
- The master component of AVC-LAN is the radio receiver assy with a resistance (60 - 80 Ω), which is necessary for communication.
- When short circuit or circuit breakdown occurs in the AVC-LAN circuit, the audio system does not operate normally due to the communication cutoff.
- DIAGNOSIS FUNCTION
- The audio system has diagnosis function (The diagnosis result is displayed on the LCD of the radio receiver assy). (Radio receiver with CD changer control function)
- The component code (physical address), or three-digit number (in hexadecimal) is set for each component comprising AVC-LAN.
- The logical address, or two-digit number (in hexadecimal) is set for each function and component unit in each component.
- RADIO WAVE BAND
- The radio wave bands used in radio broadcasting are as follows:
- SERVICE AREA
- 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.
- 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.
- RECEPTION PROBLEMS NOTE: Besides the problem of static, there are also the problems called "fading", "multipath" and "fade out". These problems are caused not by electrical noise but by the nature of the radio waves themselves.
- 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".
- 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 interferes with other signals which is to be received directly.
- 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".
- Fading
- NOISE PROBLEMS
- It is very important for noise troubleshooting to understand a customer's claim clearly. Use the following table to diagnose the phenomenon.NOISE PROBLEMS
Radio wave Condition in which noise occurs Probable cause AM Noise occurs at a specific place. Strong possibility of foreign noise. Noise occurs when listening to faint broadcasting. The same program may be broadcasted from some local stations. If the program is the same, one of those may be tuned in. Noise occurs only at night. Strong possibility of beat from a distant broadcasting. FM Noise occurs at a specific place during driving. Strong possibility of muitipath noise and fading noise caused by changes of FM frequency. 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. - Matters that require attention when checking:
- Noise coming into the radio usually has no harm for practical use as the noise protection is taken and it is hardly thinkable for an extremely loud noise to come in. When extremely loud noise comes into the radio, check if the grounding is normal where the antenna is installed.
- Check if all the regular noise prevention parts are properly installed and if there is any installation of non-authorized parts and non-authorized wiring.
- If you leave the radio out of tune (not tuning), it is easy to diagnose the phenomenon as noise occurs frequently.
- Antenna and noise:
Electronic signal received by the antenna will reach to the radio transmitting through the core wire of the coaxia cable. Any noise wave other than radio wave is mixed into this core wire, that naturally causes noise in the radio and poor sound quality. In order to prevent these noises from mixing into the radio, the core wire inside the coaxial cable is covered with a mesh wire called shield wire. This shield wire shelters the noise and transmits it to the ground, thus preventing noise from mixing in. If this shield wire has grounding failure, that causes noise.
- Choke coil and noise:
The choke coil is connected in the rear window defogger circuit. This is connected so to prevent noise from mixing into the radio by making the noise current included ion the power source of the rear window defogger flow to the ground.
- It is very important for noise troubleshooting to understand a customer's claim clearly. Use the following table to diagnose the phenomenon.
- COMPACT DISC PLAYER
- 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) disc available for the CD player.
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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.