LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2009 >> LS 600hL >> Repair and Diagnosis >> External Pages >> Different car >> Section 51 (Cellular Communication) >> LEXUS Link System >> DTC 4-7: EMERGENCY, VOL+ or VOL- Button has Connection Error >> Inspection Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Inspection Procedure

WARNING: This page is about a different car, the 2008 Lexus LS 600hL. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK HARNESS AND CONNECTOR (MAYDAY ECU - MAP LIGHT (MAYDAY SWITCH)) 
    1. Disconnect the R23 ECU connector.
    2. Disconnect the X4 map light connector.
    3. Measure the resistance according to the value(s) in the table below.

    Standard resistance 

    TESTER CONNECTION SPECIFIED CONDITION CHART

    Tester Connection Condition Specified Condition
    R23-5 (SIG1) - X4-30 (SIG1) Always Below 1 Ω
    R23-12 (SIG-) - X4-32 (GND3) Always Below 1 Ω
    Fig 1: Checking Harness And Connector (Mayday ECU - MAP Light (Mayday Switch))
    G04945815Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR THEN CLEAR HISTORIC DTC 

    OK: Go to next step 

  2. INSPECT MAP LIGHT ASSEMBLY (MAYDAY SWITCH) 
    1. Remove the map light (see REMOVAL )
    2. Measure the resistance according to the value(s) in the table below.

    Standard resistance 

    TESTER CONNECTION SPECIFIED CONDITION CHART

    Tester Connection Condition Specified Condition
    30 (SIG1) - 32 (GND3) EMERGENCY button is pressed 305 to 313 Ω
    30 (SIG1) - 32 (GND3) VOL+ button is pressed 812 to 831 Ω
    30 (SIG1) - 32 (GND3) VOL- button is pressed 1811 to 1848 Ω
    Fig 2: Inspecting MAP Light Assembly (Mayday Switch)
    G04945810Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE MAP LIGHT ASSEMBLY (MAYDAY SWITCH) THEN CLEAR HISTORIC DTC 

    OK: REPLACE MAYDAY ECU TOGETHER WITH MAYDAY BATTERY AND THEN PERFORM REGISTRATION