Toyota Sequoia (2005). Manual — part 542
DID9O–01
AUDIO SYSTEM Check Sheet
Inspector’s name:
Customer’s Name
VIN
Production Date
Licence Plate No.
Odometer Reading
/ /
km
mile
Frequency of Problem Occurrence
/ /
Constant
Intermittent ( Times a day)
Brought–in Date
Problem
Symptom
Radio
Radio receiver assy
Parts name
DTC (1st time).
DTC (2nd time).
Switch
Noise
CD
Stereo component amplifier assy
DTC
Check
Multi–display controller
Rear seat audio controller
–
DIAGNOSTICS
AUDIO SYSTEM
DI–1963
2157
CUSTOMER PROBLEM ANALYSIS CHECK
DID9P–01
30 kHz
300 kHz
3 MHz
30 MHz
300 MHz
LF
MF
HF
VHF
AM
FM
Frequency modulation
Frequency
Designation
Radio wave
Modulation
Amplitude modulation
BE2818
FM (Stereo)
FM (Monaural)
AM
BE2819
Ionosphere
Phasing
DI–1964
–
DIAGNOSTICS
AUDIO SYSTEM
2158
IDENTIFICATION OF NOISE SOURCE
1.
RADIO WAVE BAND
The radio wave bands used in radio broadcasting are as follows:
LF: Low Frequency
MF: Medium Frequency
HF: High Frequency
VHF: Very High Frequency
2.
SERVICE AREA
There is a great difference in the size of the service areas for
AM and FM broadcasting. Sometimes an FM stereo broadcast
cannot be received even though AM can be received very clear-
ly.
FM stereo has the smaller service area, it also picks up static
and other types of interference (”noise”) easily.
3.
RECEPTION PROBLEMS
HINT:
Besides the problem of static, there are other problems, such as ”phasing”, ”multipath” and ”fade out”. These
problems are caused not by electrical noise but by the nature of the radio waves themselves.
(a)
Phasing
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 ion-
osphere at night. These radio waves then interfere with
the signals that reach the vehicle’s antenna directly from
the same transmitter. This type of interference is called
”phasing”.
BE2820
Multipath
BE2821
Fade Out
–
DIAGNOSTICS
AUDIO SYSTEM
DI–1965
2159
(b)
Multipath
Interference caused by reflection of radio waves against
obstructions is called ”Multipath”. Multipath occurs when
radio signals emitted from the broadcast transmitter an-
tenna are reflected against tall buildings or mountains
and interferes with other signals which are to be received
directly.
(c)
Fade Out
FM radio wave tends to be reflected against obstructions
such as tall buildings or mountains because FM frequen-
cy is higher than AM. For this reason, FM signals often
seem to gradually disappear or fade away as the vehicle
goes behind those obstructions. This phenomenon is
called ”fade out”.
4.
NOISE PROBLEMS
It is very important for technicians to clearly understand a customer’s claim about noise. Use the following
table to diagnose the phenomena.
Radio wave
Condition in which noise occurs
Probable cause
Noise occurs at a specific place.
Strong possibility of foreign noise.
AM
Noise occurs when listening to faint broadcasting.
The same program may be broadcasted from some local sta-
tions. 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 multipath noise and fading noise caused
by changes of FM frequency.
HINT:
If the condition when the noise occurs does not meet any of the above, find out the cause based on ”Recep-
tion Problems”. Refer to the description about Multipath and Phasing mentioned previously.
DI–1966
–
DIAGNOSTICS
AUDIO SYSTEM
2160
5.
Identify the condition in which the noise occurs, and check the noise filter on the related part.
Condition in which noise occurs
Noise Source
Depressing the acceleration pedal increases the noise, and stopping the
engine stops the noise immediately.
Generator
Noise occurs during A/C or the heater operation.
Blower motor
Rapid acceleration while driving on an unpaved road or after the ignition
switch is turned on makes noise.
Fuel pump
Pressing and then releasing the horn switch, and keeping pressing the horn
switch makes unusual noise.
Horn
Quiet noise is heard while the engine is running, but stops with the engine.
Ignition
Noise occurs synchronously with the turn signal flash.
Flasher
Noise occurs during window washer operation.
Washer
Noise occurs while the engine is running, and it continues even after the en-
gine stops.
Engine coolant temperature sensor
Noise occurs during wiper operation.
Wiper
Noise occurs when the brake pedal is depressed.
Stop light switch
Others.
Static electricity stored on the vehicle
Reference:
Make sure first that there is no noise from outside. Failing to do so makes the noise source detec-
tion difficult and leads to misdiagnosis.
The noise should be removed in descending order of loudness.
Tuning the radio so that no station is received wakes the noise more noticeable, making the rec-
ognition of the phenomenon easier.
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