DTC 4-7

CELLULAR COMMUNICATION: LEXUS LINK SYSTEM: 4-7: EMERGENCY, VOL+ or VOL- Button has Connection Error

DTC 4-7 - EMERGENCY, VOL+ or VOL- Button has Connection Error

DESCRIPTION

This DTC is output when one of the following occurs: 1) the mayday ECU assembly is malfunctioning; 2) the mayday switch assembly is malfunctioning; or 3) the wire harness between the mayday ECU assembly and the roof console box assembly is open or short.






WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

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




(a) Disconnect the M16 ECU connector.
(b) Disconnect the O2 roof console box connector.
(c) Measure the resistance of the wire harness side connectors.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
2. INSPECT ROOF CONSOLE BOX ASSEMBLY (MAYDAY SWITCH ASSEMBLY)




(a) Remove the roof console box assembly.
(b) Measure the resistance of the switch when each switch is pressed.
Standard resistance:





NOTE:
If replacement of the ECU is necessary, replace the mayday battery (backup battery) together with the ECU. After the replacement, register the ECU Programming and Relearning.

NG -- REPLACE ROOF CONSOLE BOX ASSEMBLY
OK -- REPLACE MAYDAY ECU ASSEMBLY