WARNING: This page is about a different car, the 2003 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.

Fig 1: Inspection Connector On Wire Harness Side

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OVERHEAD JUNCTION BLOCK ASSEMBLY CONDITION

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

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

Overhead J/B side:

INSPECT OVERHEAD JUNCTION BLOCK ASSEMBLY

Fig 2: Identifying Wire Harness

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OVERHEAD JUNCTION BLOCK ASSEMBLY CONNECTION

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.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Section 394 (Overhead Junction Block): Inspection

Use the Manual With the Right Hardware

When to See a Mechanic