1991 LEXUS SC400 audio

4RadioANY SPEAKER DOES NOT WORK
(EXCEPT WOOFER)
A. without CD player type
Is there continuity between the following terminals
with connector disconnected?

Fr: Radio receiver assembly A1±FR speaker 1
Radio receiver assembly A5±FR speaker 2

FL: Radio receiver assembly A2±FL speaker 1
Radio receiver assembly A6±FL speaker 2

RR: Radio receiver assembly C1±RR speaker 1
Radio receiver assembly C3±RR speaker 2

RL: Radio receiver assembly C2±RL speaker 1
Radio receiver assembly C6±RL speaker 2
Is there continuity between the following terminals
with connector disconnected?

FR: Radio receiver assembly A1±ground
Radio receiver assembly A5±ground

FL: Radio receiver assembly A2±ground
Radio receiver assembly A6±ground

RR: Radio receiver assembly C1±ground
Radio receiver assembly C3±ground

RL: Radio receiver assembly C2±ground
Radio receiver assembly C6±ground Wire harness faulty


(The wire harness for the FR speaker passes
through the transceiver, so the transceiver side
should be checked) Wire harness faulty


(The wire harness for the FR speaker passes
through the transceiver, so the transceiver side
should be checked)
Speaker faulty. Radio receiver assembly faulty.
Is tape player operating normally?
Temporarily install another speaker.
Finctions OK?
Radio receiver assembly faulty.
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±225
WhereEverybodyKnowsYourName

Is there continuity between the following terminals
with connector disconnected?

Fr: Radio receiver assembly B1±FR speaker 1
Radio receiver assembly B5±FR speaker 2

FL: Radio receiver assembly B2±FL speaker 1
Radio receiver assembly B6±FL speaker 2

RR: Radio receiver assembly B3±RR speaker 1
Radio receiver assembly B4±RR speaker 2

RL: Radio receiver assembly B8±RL speaker 1
Radio receiver assembly BP±RL speaker 2
Is there continuity between the following terminals
with connector disconnected?

FR: Radio receiver assembly B1±ground
Radio receiver assembly B5±ground

FL: Radio receiver assembly B2±ground
Radio receiver assembly B6±ground

RR: Radio receiver assembly B3±ground
Radio receiver assembly B4±ground

RL: Radio receiver assembly B8±ground
Radio receiver assembly B9±ground Wire harness faulty


(The wire harness for the FR speaker passes
through the transceiver, so the transceiver side
should be checked) Wire harness faulty

(The wire harness for the FR speaker passes
through the transceiver, so the transceiver side
should be checked)
Speaker faulty.
Radio receiver assembly faulty.
Is tape player operating normally?
Wire harness faulty.
Temporarily install another speaker.
Functions OK?
Is there continuity between the following terminals
with connector disconnected?

FR: Radio receiver assembly A7±Power
amplifier A1

FL: Radio receiver assembly A6±Power
amplifier A2

RR: Radio receiver assembly A15±Power
amplifier A7

RL: Radio receiver assembly A14±Power
amplifier A8
Is there continuity between the following terminals
with connector disconnected?

FR: Radio receiver assembly A7±ground

FL: Radio receiver assembly A6±ground

RR: Radio receiver assembly A15±ground

RL: Radio receiver assembly A14±ground Wire harness faulty.
only for vehicles with cellular phone
B. with CD player type BE±226
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

Temporarily install another amplifier.
Functions is OK?Power amplifier faulty.
Radio receiver assembly faulty.
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±227
WhereEverybodyKnowsYourName

5RadioVOLUME FAINT (EXCEPT WOOFER)
A. without CD player type
*Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly D3±ground
Is tape player operating normally? Radio receiver assembly faulty.
Power switch faulty.
Wire harness faulty.
Radio receiver assembly faulty.
When the volume switch is turned from minimum
to maximum, does resistance between terminals
B1±B3 of radio receiver assembly change from 0
to 50 k
?
B. with CD player type
*Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly D3±ground
Is tape player operating normally? Radio receiver assembly faulty.
Power switch faulty.
Wire harness faulty.
Radio receiver assembly faulty. When the volume switch is turned from minimum
to maximum, does resistance between terminals
B1±B3 of radio receiver assembly change from 0
to 50 k
?
Power amplifier faulty.
Temporarily install another power amplifier
Function is OK?
BE±228±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

6RadioWOOFER DOES NOT WORK
A. without CD player type
Is there battery voltage between the following termi-
nals with connector connected?

Woofer amplifier 3 ± ground

Woofer amplifier 4 ± ground
Is there continuity between the following terminals
with connector disconnected?

Woofer amplifier 9 ± Woofer 2

Woofer amplifier 10 ± Woofer 1
Is there continuity between the following terminals
with connector disconnected?

Woofer amplifier 9 ± ground

Woofer amplifier 10 ± ground Is there continuity between the following termi-
nals with connector connected?


Radio receiver assembly A9±Woofer amplifier 6
Wire harness faulty.
Wire harness faulty. Wire harness faulty.
Wire harness faulty. Woofer faulty.
Is there continuity between the following termi-
nals with connector disconnected?


Woofer amplifier 7±ground
Is there battery positive between the following
terminals with connector connected?


Woofer amplifier 7±ground
Temporarily install another woofer.
Functions OK?
Radio receiver assembv faulty. Radio receiver assembly faulty.
Is tape player operating normally?
Radio receiver
assembly faulty.Wire harness faulty.
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±229
WhereEverybodyKnowsYourName

B. with CD player type
HINT: The part names and terminals indicated in brackets ( ) are for model\
s with a Nakamichi system.
Wire harness faulty.
Wire harness faulty. Wire harness faulty.
Wire harness faulty.
Wire harness faulty.
Woofer faulty.
Radio receiver assembly faulty.
Is tape player operating normally?
Radio receiver assembly faulty.
Temporarily install another woofer.
Functions OK? 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 9 (Power amplifier C9) ±Woofer 2

Woofer amplifier10 (Power amplifier C10) ±Woofer 1Is 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) ±ground

Woofer amplifier10 (Power amplifier C10) ±ground
Is there battery positive between the following
terminals with connector connected?


Woofer amplifier 3 (Power amplifier C3) ±ground

Woofer amplifier4 (Power amplifier C4) ±ground
BE±230±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

7RadioWOOFER VOLUME FAINT
A. without CD player type
Wire harness faulty.Wire harness faulty.
Radio receiver assembly faulty.
Is tape player operating normally?
Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly D1±ground

Radio receiver assembly D5±ground
Woofer amplifier faulty.
Is there continuity between the following terminals
with connector disconnected?


Radio receiver amplifier D1 ± Woofer amplifier 1

Radio receiver amplifier D5 ± Woofer amplifier 5
Radio receiver assembly faulty. Temporarily install another woofer amplifier.
Functions OK?
B. with CD player type
HINT: The part names and terminals indicated in brackets ( ) are for model\
s with a Nakamichi system.
Wire harness faulty. Wire harness faulty. Radio receiver assembly faulty.
Is tape player operating normally?
Is there continuity between the following terminals
with connector disconnected?


Radio receiver assembly D1±ground

Radio receiver assembly D5±ground
Woofer amplifier faulty.
Is there continuity between the following terminals
with connector disconnected?


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

Radio receiver amplifier D5 ± Woofer amplifier 5
(Power amplifier C5)
Radio receiver assembly faulty. Temporarily install another woofer amplifier.
Functions OK?
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±231
WhereEverybodyKnowsYourName

8RadioRECEPTION POOR
Antenna cord faulty.Poor signals, poor location.
Problem with radio wave signals or location?
Go to No. 32. Check if antenna cord is OK?
Radio receiver assembly faulty.
9RadioPRESET MEMORY DISAPPEARS
Wire harness or connector faulty.
Radio receiver assembly faulty. Is terminal A4 of radio receiver assembly
properly connected?
BE±232±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName