Section 540 (Overhead Junction Block): Inspection

WARNING: This page is about a different car, the 2004 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.

INSPECT OVERHEAD JUNCTION BLOCK ASSEMBLY

Disconnect the connector from the overhead J/B, and inspect the connector on the wire harness side, as shown.

If continuity is not as specified, repair or replace the wire harness.

Fig 1: Identifying Connector From Overhead J/B

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

TESTER CONDITION SPECIFICATION

Tester connection	Condition	Specified condition
1 - Ground	Always	Continuity
8 - Ground	Always	Battery positive voltage
11 - Ground	Ignition switch OFF or ACC	No voltage
11 - Ground	Ignition switch ON	Battery positive voltage

Overhead J/B side: INSPECT OVERHEAD JUNCTION BLOCK ASSEMBLY

Fig 2: Identifying Overhead Junction Block Assembly

OVERHEAD JUNCTION BLOCK CIRCUIT CONTINUITY SPECIFICATION CHART

Circuit name	Tester connection	Specified condition
Power source circuit	A8-B6-E6	Continuity
Power source circuit	A11-B8-G1	Continuity
Ground circuit	A1-B2-E8-D3-F1	Continuity
Microphone circuit	A2-B10-G4	Continuity
Microphone circuit	A3-B9-G2	Continuity
Mayday switch circuit	A13-B7-F4	Continuity
Mayday switch circuit	A7-B4-F3	Continuity
Mayday switch circuit	A14-B3-F12	Continuity

If continuity is not as specified, replace the overhead J/B assembly.