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.