Inspection Procedure

WARNING: This page is about a different car, the 2004 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.

CHECK TELEPHONE SWITCH ASSY (MAYDAY SWITCH)
1. Disconnect the mayday switch connector.
2. Check that the continuity exists between each terminals of switch when each switch is pressed.
  OK:
  
  Fig 1: Tester Specification Table - Mayday Switch
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 2: Identifying Mayday Switch Connector Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. NG: REPLACE TELEPHONE SWITCH ASSY (MAYDAY SWITCH)
2. OK: Go to next step.
CHECK HARNESS AND CONNECTOR (BETWEEN TELEPHONE ECU (MAYDAY ECU) AND TELEPHONE SWITCH (MAYDAY SWITCH) ASSY) (See HOW TO PROCEED WITH TROUBLESHOOTING )
1. NG: REPAIR OR REPLACE HARNESS OR CONNECTOR
2. OK: Go to next step.
  REPLACE TELEPHONE ECU ASSY (MAYDAY ECU) (See HOW TO PROCEED WITH TROUBLESHOOTING )