Inspection Procedure

WARNING: This page is about a different car, the 2007 Lexus GX 470. However, it is still accessible from the selected car via links, so may be relevant.

CHECK WIRE HARNESS (ECU - ROOF CONSOLE BOX ASSEMBLY (MAYDAY SWITCH ASSEMBLY))

Fig 1: Identifying Roof Console Box & Mayday ECU Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Disconnect the M16 ECU connector.
Disconnect the O2 roof console box connector.
Measure the resistance of the wire harness side connectors.
Standard resistance

RESISTANCE SPECIFICATION

Tester Connection	Specified Condition
M16-4 (IND1) - O2-16 (IND1)	Below 1 Ω
M16-4 (IND1) or O2-16 (IND1) - Body ground	10 kΩ or higher

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step

REPLACE ROOF CONSOLE BOX ASSEMBLY
1. Temporarily replace the roof console box assembly (See REMOVAL ) with a new or normally functioning one.
2. Check that the system operates normally.
  OK:
  
  Red LED operates normally.
  
  NOTE: If replacement of the ECU is necessary, replace the mayday battery (backup battery) together with the ECU. After the replacement, register the ECU (See REGISTRATION ).
  
  NG: REPLACE MAYDAY ECU ASSEMBLY (See REMOVAL )
OK: END