Inspection Procedure

WARNING: This page is about a different car, the 2003 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.

Check Mayday switch (Overhead J/B).

PREPARATION:

Disconnect the Mayday switch connector.

CHECK:

Check that the continuity exists between terminals of Mayday switch when each switch is pressed.

OK:

TESTER CONNECTION SPECIFICATION

Switch position	Tester connection	Specified condition
Service Play back Record	1 - 2	Continuity
Emergency Volume UP Volume DOWN	2 - 3	Continuity

Fig 1: Checking Mayday Switch

NG : Replace the Mayday switch [overhead J/B).
OK : Go to next step.

Check for open and short circuit in harness and connector between telephone ECU (Mayday ECU) and Mayday switch (See HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE ).
1. NG : Replace or repair wire harness connector.
2. OK : Replace the telephone ECU (Mayday ECU) (See HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE ).
HINT:

If DTC is not cleared even through the Mayday ECU is replaced, replace the Mayday Assembly (Transceiver, Back-up battery, Bus buffer ECU and Mayday ECU).