Lexus RX300 (MCU15). Manual — part 150
BE1YN–01
I04188
Wire Harness Side
I08150
Connector ”B”
Connector ”C”
Connector ”A”
Wire Harness Side
–
BODY ELECTRICAL
AUDIO SYSTEM (Europe)
BE–147
LEXUS RX300 (RM785E)
INSPECTION
1.
INSPECT CD AUTO CHANGER CIRCUIT
Disconnect connectors from CD auto changer and inspect the
connector on the wire harness side.
Tester connection
Condition
Specified condition
8 – Ground
Constant
Continuity
12 – Ground
Ignition switch LOCK
No voltage
12 – Ground
Ignition switch ACC or ON
Battery positive voltage
5 – Ground
Constant
Battery positive voltage
If the circuit is not as specified, inspect the circuits connected
to other parts.
HINT:
S
Check the wire harness between the radio receiver as-
sembly and the CD auto changer.
S
Since the signals to and from the MUTE, R
–
, R
+
, L
–
, L
+
,
TX
–
and TX
+
terminals are serial signals, they cannot or-
dinarily be measured with a tester.
2.
INSPECT POWER AMPLIFIER CIRCUIT
Disconnect the connector from power amplifier and inspect the
connector on the wire harness side.
I07332
Connector ”B”
Connector ”C”
Connector ”A”
Wire Harness Side
BE–148
–
BODY ELECTRICAL
AUDIO SYSTEM (Europe)
LEXUS RX300 (RM785E)
Tester connection
Condition
Specified condition
A6 – Ground
Constant
Continuity
A3 – Ground
Ignition switch LOCK and radio switch ON
No voltage
A3 – Ground
Ignition switch ACC or ON and radio switch ON
Battery positive voltage
A4 – Ground
Constant
Battery positive voltage
If the circuit is not as specified, inspect the circuits connected
to other parts.
3.
INSPECT RADIO RECEIVER ASSEMBLY CIRCUIT
Disconnect the connectors from the radio receiver assembly,
and inspect the connector on the wire harness side.
Tester connection
Condition
Specified condition
A2 – Ground
Constant
Continuity
A4 – Ground
Constant
Battery positive voltage
A1 – Ground
Ignition switch LOCK
No voltage
A1 – Ground
Ignition switch ACC or ON
Battery positive voltage
HINT:
Check the wire harness between radio receiver assembly and
the CD auto changer, between radio receiver assembly and
power amplifier.
BE1YO–01
30 kHz
300 kHz
3 MHz
30 MHz
300 MHz
LF
MF
HF
VHF
AM
FM
Frequency modulation
Frequency
Designation
Radio wave
Modulation
Amplitube modulation
BE2818
FM (Stereo)
FM (Monaural)
AM
BE2819
Fading
lonosphere
–
BODY ELECTRICAL
AUDIO SYSTEM (Except Europe)
BE–149
LEXUS RX300 (RM785E)
AUDIO SYSTEM (Except Europe)
DESCRIPTION
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 are great differences in the size of the service area for AM
and FM monaural. Sometimes FM stereo broadcasts cannot be
received even through AM can be received in 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.
3.
RECEPTION PROBLEMS
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.
S
Fading
Besides electrical interference, AM broadcasts are
also susceptible to other types of interference, es-
pecially 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”.
BE2820
Multipath
BE2821
Fade Out
AM
FM
Noise occurs at a specific place.
Strong possibility of foreign noise.
Noise occurs when listening to
faint broadcasting.
Noise occurs only at night.
Noise occurs while driving and
at a specific place.
There is a case that the same program is broadcasted
from each local station and that may be the case you are
listening different station if the program is the same.
Strong possibility of the beat from a distant broadcasting.
Strong possibility of multipath noise and fading noise
caused by the changes of FM waves.
BE–150
–
BODY ELECTRICAL
AUDIO SYSTEM (Except Europe)
LEXUS RX300 (RM785E)
S
Multipath
One type of interference caused by the bounce of
radio waves off of obstructions is called ”multipath”.
Multipath occurs when a signal from the broadcast
transmitter antenna bounces off buildings and
mountains and interferes with the signal that is re-
ceived directly.
S
Fade Out
Because FM radio waves are of higher frequencies
than AM radio waves, they bounce off buildings,
mountains, and other obstructions. For this reason,
FM signals often seem to gradually disappear or
fade away as the vehicle goes behind a building or
other obstruction. This is called ”fade out”.
4.
NOISE PROBLEMS
(a)
Questionnaire for noise:
It is very important for noise troubleshooting to have good
understanding of the claims from the customers, so make
the best use of following questionnaire and diagnose the
problem accurately.
HINT:
In the case that the noise occurrence condition does not meet
any of the above questionnaire, check based on the ”Reception
problems”.
Refer to above descriptions for multipath and fading.
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