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 is malfunctioning; 2) the map light assembly is malfunctioning; 3) the mayday switch is malfunctioning; or 4) the wire harness between the mayday ECU and the map light is open or short.






WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK WIRE HARNESS (MAYDAY ECU - MAP LIGHT (MAYDAY SWITCH))





(a) Disconnect the U46 ECU connector.
(b) Disconnect the W8 map light connector.
(c) Measure the resistance of the wire harness side connectors.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS AND CONNECTOR THEN CLEAR HISTORIC DTC
OK -- Continue to next step.
2. INSPECT MAYDAY SWITCH ASSEMBLY





(a) Remove the map light.
(b) Remove the mayday switch from the map light.
(c) Measure the resistance of the switch when each switch is pressed.
Standard resistance:






NG -- REPLACE MAYDAY SWITCH ASSEMBLY THEN CLEAR HISTORIC DTC
OK -- Continue to next step.
3. INSPECT MAP LIGHT ASSEMBLY





(a) Install the mayday switch to the map light.
(b) Measure the resistance of the switch when each switch is pressed.
Standard resistance:






NG -- REPLACE MAP LIGHT ASSEMBLY THEN CLEAR HISTORIC DTC
OK -- REPLACE MAYDAY ECU TOGETHER WITH MAYDAY BATTERY AND THEN PERFORM REGISTRATION