1991 LEXUS SC400 audio

B. with CD player type
Is there continuity between the following terminals
with connector disconnected?

Fr: Power amplifier B1±FR speaker 1
Power amplifier B5±FR speaker 2

FL: Power amplifier B2±FL speaker 1
Power amplifier B6±FL speaker 2

RR: Power amplifier B3±RR speaker 1
Power amplifier B4±RR speaker 2

RL: Power amplifier B8±RL speaker 1
Power amplifier B9±RL speaker 2
Is there continuity between the following terminals
with connector disconnected?

FR: Power amplifier B1±ground
Power amplifier B5±ground

FL: Power amplifier B2±ground
Power amplifier B6±ground

RR: Power amplifier B3±ground
Power amplifier B4±ground

RL: Power amplifier B8±ground
Power amplifier 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?
Temporarily install another speaker.
Functions OK?
Wire harness faulty.
Wire harness faulty.
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
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±241
WhereEverybodyKnowsYourName

Radio receiver assembly faulty.Power amplifier faulty.
Temporarily install another power amplifier.
Function is OK?
BE±242±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

15Tape playerVOLUME FAINT (EXCEPT WOOFER)
A. without CD player type
Is radio operating normally?Radio receiver assembly faulty.
When the volume switch is turned from minumum to
maximum, does resistance between terminal B1±B3
of radio receiver assembly change from 0 to 50 k ? Power switch faulty.
Wire harness faulty.
Is there battery voltage between the following ter-
minals with connector disconnected?

Radio receiver assembly D3 ± ground
Radio receiver assembly faulty.
B. with CD player type
Is radio operating normally? Radio receiver assembly faulty.
When the volume switch is turned from minumum to
maximum, does resistance between terminal B1±B3
of radio receiver assembly change from 0 to 50 k ? Power switch faulty.
Wire harness faulty.
Is there battery voltage between the following ter-
minals with connector disconnected?

Radio receiver assembly D3 ± ground
Radio receiver assembly faulty. Power amplifier faulty.
Temporarily install another power amplifier.
Function is OK?
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±243
WhereEverybodyKnowsYourName

16Tape playerWOOFER DOES NOT WORK
A. without CD player type
Is radio operating normally?Radio receiver assembly faulty.
Wire harness faulty.
Is there battery voltage between the following ter-
minals with connector connected?


Woofer amplifier 3 ± ground

Woofer amplifier 4 ± ground
Is there battery voltage between the following ter-
minals with connector connected?

Woofer amplifier 6 ± ground
Is there continuity between the following termi-
nals with connector disconnected?

Woofer amplifier 7 ± ground
Wire harness faulty.
Wire harness faulty.
Woofer faulty.
Wire harness faulty.
Is there continuity between the following terminals
with connector disconnected?

Radio receiver assembly A9 ± Woofer amplifier 6
Radio receiver
assembly faulty. Wire harness faulty.
Is there continuity between the following terminals
with connector connected?

Woofer amplifier 9 ± Woofer 2

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

Woofer amplifier 9 ± ground

Woofer amplifier 10 ± ground
Temporarily install another woofer.
Functions OK? Radio receiver assembly faulty
BE±244±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

B. with CD player type
HINT: The part names and terminals indicated in brackets ( ) are for model\
s with a Nakamichi system.
Is radio operating normally?Radio receiver assembly faulty.
Woofer faulty.
Wire harness faulty.
Is there battery voltage between the following
terminals with connector connected?

Woofer amplifier 3 (Power amplifier C3) ± ground

Woofer amplifier 4 (Power amplifier C4) ± ground
Temporarily install another woofer.
Functions OK? Radio receiver assembly faulty Wire harness faulty.
Wire harness faulty.
Wire harness faulty.
Wire harness faulty.
Is there continuity between the following terminals
with connector disconnected?


Woofer amplifier 9 (Power amplifier C9) ±
Woofer 2

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

Woofer amplifier 9 (Power amplifier C9) ± ground

Woofer amplifier 10 (Power amplifier C10) ±
ground
Is there battery voltage between the following
terminals with connector connected?


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

Woofer amplifier 7 (Power amplifier C7) ± ground
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±245
WhereEverybodyKnowsYourName

17Tape playerWOOFER VOLUME FAINT
A. without CD player type
Is radio operating normally?Radio receiver assembly faulty.
Wire harness faulty.
Is there continuity between the following terminals
with connector connected?

Radio receiver assembly D1 ± Woofer amplifier 1

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


Radio receiver assembly D1 ± ground

Radio receiver assembly D5 ± ground
B. with CD player type
HINT: The part names and terminals indicated in brackets ( ) are for model\
s with a Nakamichi system.
Is radio operating normally?
Radio receiver assembly faulty.
Wire harness faulty.
Is there continuity between the following terminals
with connector connected?

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

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

Radio receiver assembly D1 ± ground

Radio receiver assembly D5 ± ground
BE±246±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

18Tape playerSOUND QUALITY POOR
A. without CD player type
Is radio operating normally?Is speaker properly installed?
Temporarily install another speaker.
Functions OK?
Radio receiver assembly faulty. Operates normally after cleaning the heads?
Head dirty.
Radio receiver
assembly faulty.
Speaker installation faulty.
Speaker faulty.
B. with CD player type
Is speaker properly installed?
Temporarily install another speaker.
Functions OK?
Radio receiver assembly faulty. Speaker installation faulty.
Speaker faulty.
Power amplifier faulty.
Head dirty. Radio receiver as-
sembly faulty.
Temporarily install another power amplifier.
Functions OK?
Is radio operating normally?
Operates normally after cleaning the heads?
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±247
WhereEverybodyKnowsYourName

19Tape playerVOLUME REMAINS AT MAXIMUM LEVEL
A. without CD player type
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 minu-
mum to maximum, does resistance between
terminal 11±14 of power switch change from 0
to 50 k
?
B. with CD player type
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 minumum
to maximum, does resistance between terminal
11±14 of power switch change from 0 to 50 k
?
BE±248±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName