Toyota Sequoia (2005). Manual - part 557

I28506

Stereo Component 
Amplifier Assy

Radio Receiver Assy

TX+ S10

R4

V

P

TX– S10

R4

TX+

TX–

20

5

19

15

–

DIAGNOSTICS

AUDIO SYSTEM

DI–2023

2217

AVC–LAN circuit (Radio receiver assy – stereo component ampli-
fier)

CIRCUIT DESCRIPTION

Each unit of the audio system connected to the AVC–LAN (communication bus) transfers the signal of each
switch by communication.
When a short to +B or short to ground occurs in this AVC– LAN, the audio system will not function normally
as communication is discontinued.
In this AVC–LAN, the radio receiver assy becomes the master of the communication, and the radio receiver
assy has resistance necessary for communication.

WIRING DIAGRAM

DIDA1–01

I28765

Radio Receiver Assy 
Wire Harness View:

TX–

TX+

R4

DI–2024

–

DIAGNOSTICS

AUDIO SYSTEM

2218

INSPECTION PROCEDURE

1

Inspect radio receiver assy.

PREPARATION:
Disconnect the radio receiver assy connector.
CHECK:
Measure the resistance according to the value(s) in the table
below.
OK:

Symbol 

(Tester connection)

Condition

Specified condition

TX+(R4–5) – TX– (R4–15)

Always

60 to 80 

Ω

NG

Replace radio receiver assy.

OK

I28739

Radio Receiver Assy 
Wire Harness View:

TX–

TX+

R4

I28752

Stereo Component Amplifier Assy:

TX–

TX+

S10

–

DIAGNOSTICS

AUDIO SYSTEM

DI–2025

2219

2

Check harness and connector (Radio receiver assy – Stereo component amplifi-
er assy).

PREPARATION:
Disconnect the stereo component amplifier assy connector.
CHECK:
Measure the resistance according to the values in the table be-
low.
OK:

Symbol (Tester connection)

Specified condition

TX+ (R4–5) – TX+ (S10–20)

Below 1 

Ω

TX– (R4–15) – TX– (S10–19)

Below 1 

Ω

TX+ (R4–5) – Body ground

10 k

Ω 

or higher

TX– (R4–15) – Body ground

10 k

Ω 

or higher

NG

Repair or replace harness or connector.

OK

Proceed to next circuit inspection shown on problem symptoms table or diagnostic trouble code
chart (See page 

DI–1967

 or 

DI–1979

).

DI–2026

–

DIAGNOSTICS

AUDIO SYSTEM

2220

Sound quality is bad in all modes (Volume is too low)

INSPECTION PROCEDURE

1

Adjust sound quality.

CHECK:
Set ”BASS” and ”TREB” to the initial values and check if sounds is normal.
OK:

Malfunction disappears.

OK

System is OK.

NG

2

Replace stereo component amplifier assy.

Replace the stereo component amplifier assy and check if it operates normally.
OK:

Malfunction disappears.

NG

Replace radio receiver assy.

OK

End.

DIDA2–01