LEXUS SC400 1991 Service Repair Manual

26CD playerWOOFER DOES NOT WORK
HINT: The part names and terminals indicated in brackets ( ) are for models\
with a Nakamichi system.
Is radio operating normally?
Is there battery voltage between the following ter-
minals with connector connected?

Woofer amplifier 3 (Power amplifier C3) ± ground

Woofer amplifier 4 (Power amplifier C4) ± ground
Woofer faultyRadio receiver assembly faulty.
Wire harness faulty.
Wire harness faulty.
Wire harness faulty.
Wire harness faulty.
Wire harness faulty.
Is there battery voltage between the following ter-
minals with connector connected?


Woofer amplifier 6 (Power amplifier C6) ± ground
Is there continuity between the following terminals
with connector disconnected?

Woofer amplifier 7 (Power amplifier C7) ± ground
Is there continuity between the following terminals
with connector disconnected?

Woofer amplifier 9 (Power amplifier C9) ±
Woofer speaker 2

Woofer amplifier 10 (Power amplifier C10) ±
Woofer speaker 1
Is there continuity between the following terminals
with connector disconnected?

Woofer amplifier 9 (Power amplifier C9) ± ground

Woofer amplifier10 (Power amplifier C10) ± ground
Temporarily install another woofer.
Functions OK?
Radio receiver assembly faulty.
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±255
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27CD playerWOOFER VOLUME FAINT
HINT: The part names and terminals indicated in brackets ( ) are for models\
with a Nakamichi system.
Is radio operating normally?
Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly D1 ± Woofer amplifier 1
(Power amplifier 1 (Power amplifier C1)

Radio receiver assembly D5 ± Woofer amplifier 1
(Power amplifier 5 (Power amplifier C5) Radio receiver assembly faulty.
Wire harness faulty.
Wire harness faulty. Woofer amplifier faulty.
Radio receiver assembly faulty. Temporarily install another woofer amplifier.
Functions OK? Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly D1 ± ground

Radio receiver assembly D5 ± ground
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28CD playerSOUND QUALITY POOR
Is radio operating normally?
Is speaker properly installed? Temporarily install another speaker
Functions OK? Temporarily install another CD auto changer.
Functions OK?
Temporarily install another power amplifier.
Functions OK? Radio receiver assembly faulty. Speaker faulty. Speaker installation faulty
Power amplifier faulty. Radio receiver assem-
bly faulty CD changer faulty.
29CD playerVOLUME REMAINS AT MAXIMUM LEVEL
Is radio operating normally?
Radio receiver assembly faulty.
Wire harness faulty.
Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly B1 ± Power switch 14

Radio receiver assembly B3 ± Power switch 11
Power switch faulty.
Radio receiver assembly faulty.
When the volume switch is turned from minimum to
maximum, does resistance between terminal 11±14
of power switch changes from 0 to 50 k
?
±
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30NoiseNOISE PRODUCED BY VIBRATION OR SHOCK
WHILE DRIVING
Is radio properly installed?
Is radio receiver assembly properly installed?
*1 Is radio power amplifier properly installed?
*2 Is woofer amplifier properly installed?*1 Is CD auto changer properly installed?
With vehicle stopped, lightly tap each part.
Is noise produced? Speaker installation faulty.
Radio receiver assembly installation faulty.
Power amplifier installation faulty.
Woofer amplifier installation faulty.
CD auto changer installation faulty. Each part faulty.
Noise produced by static electricity is accululating in the vehicle body\
.
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31NoiseNOISE PRODUCED WHEN ENGINE STARTS
Whistling noise which becomes high±pitched when
accelerator strongly depressed, disappears shortly
after engine stops.Whining noise occurs when A/C is operating.
Scratching noise occurs during sudden accel-
eration, driving on rough roads or when ignition
switch is turned on.
Clicking sound heard when horn button is
pressed, then released. Whirring/grating sound
when pushed continuously.
Murmuring sound, stops when engine stops. Tick±tock noise, occurs in coordination with
blinking of flasher.
Noise occurs during window washer operation.Scratching noise occurs while engine is running,
continues a while even after engine stops.Scraping noise in time with wiper beat.
Other type of noise. Alternator noise.
A/C noise.
Fuel gauge noise.
Horn noise.
Ignition noise. Turn signal flasher noise.
Washer noise. Water temp. gauge noise.
Wiper noise.
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32AntennaANTENNA±RELATED
Does antenna extend when radio switched ON?Wire harness faulty.
Is there battery voltage between the following
terminals with connector disconnected?


Motor antenna control relay 6 ± ground

Motor antenna control relay 14 ± ground

Motor antenna control relay 3 ± ground
Wire harness faulty.Replace fuses.
Radio receiver assembly faulty.
Check if ECU±IG, RADIO No. 1 and RADIO No.
2 fuse are OK.
ªAMº button turned ON.
Is there battery voltage between the following
terminals with connector connected?

Radio receiver assembly A9 (*A1) ± ground

Radio receiver assembly A8 ± ground

Radio receiver assembly D4 ± ground

Radio receiver assembly D10 ± ground Radio receiver side
faulty.
Motor antenna faulty.
Temporarily install another motor antenna is
radio operating normally?
Glass printed antenna faulty.
Check if glass printed antenna is OK.
Is there continuity between the following terminals
with connector disconnected?

Motor antenna control relay 4 ± ground
Continued on next page.
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Wire harness faulty.
Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly A9 (*A1) ± Motor anten-
na control relay 4

Radio receiver assembly A8 ± Motor antenna
control relay 5

Radio receiver assembly D4 ± Motor antenna
control relay 2

Radio receiver assembly D10 ± Motor antenna
control relay 12
Temporarily install another motor antenna con-
trol relay. Functions OK? Motor antenna control relay faulty.
Motor antenna control relay faulty.
±
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HORN SYSTEM
PARTS LOCATION
WIRING AND CONNECTOR DIAGRAMS
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Parts Inspection
(Horn Switch)
INSPECTION OF HORN SWITCH
INSPECT HORN SWITCH
(a) Disconnect the negative (±) terminal from the battery.
(b) Remove the left and right covers from the steering wheel.
(c) Using a torx wrench, loosen the four bolts.
(d) Pull up the horn pad and place it on the steering column as shown.
HINT: Do not disconnect the connector from the horn pad.
(e) Disconnect the connector from the slip ring.
(f) Check that there is no continuity between terminal 6 of the
connector and body ground.
(g) Check that there is continuity between terminal 6 of the connector and body ground when the horn contact plate is
pressed against the steering spoke assembly.
If continuity is not as specified, repair or replace the steering
wheel or wire harness as necessary.
(h) Install the horn pad in place and using a torx wrench, tighten the four bolts.
Torque: 7.1 N Vm (72 kgf Vcm, 62 in. Vlbf)
(i) Install the left and right covers.
(j) Connect the negative (±) terminal to the battery.
(Horn)
INSPECTION OF HORN
INSPECT HORN OPERATION
Connect the positive (+) lead from the battery to the terminal
and negative (±) lead to the horn body and check that the
horn blows.
If operation is not as specified, replace the horn.
±
BODY ELECTRICAL SYSTEM HORN SYSTEMBE±263
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HORN RELAY
HORN RELAY INSPECTION
INSPECT RELAY CONTINUITY AND OPERATION
If operation is not as specified, replace the relay.
Troubleshooting
You will find the cause of trouble more easily by properly using the tabl\
e shown below. In this table, the
numbers indicate the order of priority of the causes of trouble. Check each part in \
the order shown. If neces-
sary, replace these part.
See page
BE±4 , 21BE±264BE±263BE±263
±
Trouble
Parts
name
HAZ±HORN FuseHorn SwitchHorn SwitchHornWire Harness
\
\
Horn system does not operate 1 2 3 4 5\


\
Horns blow all the time
 


 

1
 

2
 


 

3
\


\
One horn operates but other horn does not
Operate 


 


 


 


1 


2
\
\
Horns operate abnormally  1  2 3
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