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Audio Head Unit

WARNING: This page is about a different car, the 2003 Lexus GS 430 and 2003 Lexus GS 300. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Terminals Of Audio Head Unit
G03598642Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
AUDIO HEAD UNIT REFERENCE CHART

Symbols (Terminal No.) Condition STD Voltage (V) Problem symptom when open circuit is detected.
Problem symptom when short circuit is detected.
+B <--> GND (R3-1 <--> R3-20)*1, *2 B <--> GND (R2-4 <--> R2-2)*3 Constant 10-14 Audio system does not operate.
ILL+ <--> GND (R3-2 <--> R2-2)*2 (R2-5 <--> R2-2)*3 Light control switch TAIL 10-14 Audio head unit illumination does not light up.
Fuse is blown.
ANT <--> GND (R4-5 <--> R2-2)*3 Radio switch ON 10-14 Antenna does not extend.
TX+ (R3-5)*1, *2 BUS+ (R3-10)*3 AVC-LAN Communication circuit - Audio system does not operate.
MUTE <--> GND (R3-7 <--> R3-20)*1, *2 MUTE <--> GND (R3-8 <--> R2-2)*3 Radio switch ON 5 Pop sound etc.
Audio system does not operate.
R+ <--> GND (R3-8 <--> R3-20)*1, *2 R+ <--> GND (R3-1 <--> R2-2)*1, *2 Constant 10-14 Sound from right side speaker is small.
L+ <--> GND (R3-9 <--> R3-20)*1, *2 L+ <--> GND (R3-2 <--> R2-2)*3 Constant 10-14 Sound from left side speaker is small.
ACC <--> GND (R3-11 <--> R3-20)*1, *2 ACC <--> GND (R2-1 <--> R2-2)*3 Ignition switch ACC 10-14 Audio system does not operate.
ILL- <--> GND (R3-12 <--> R2-2)*2 (R2-6 <--> R2-2)*3 Light control switch TAIL Below 0.5 Audio head unit illumination does not light up.
Fuse is blown.
ANTB <--> GND (R3-14 <--> R3-20)*2 ANTA <--> GND (R4-4 <--> R2-2)*3 Radio switch ON 10-14 Antenna does not extend.
ANTA <--> GND (R3-4 <--> R3-20)*2 Radio switch ON 10-14 Antenna does not extend.
TX-(R3-15)*1, *2 BUS-(R3-9)*3 AVC-LAN Communication circuit - Audio system does not operate.
L- <--> GND (R3-6 <--> R2-2)*3 Constant 10-14 Sound from left side speaker is small.
GND <--> Body ground (R3-20 <--> Body ground)*1, *2 GND (R2-2)*3 Constant Continuity Audio system is normal.
TX2-(R2-9) AVC-LAN Communication circuit - Audio system does not operate.
TX2+(R2-10) AVC-LAN Communication circuit - Audio system does not operate.