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

1. Disconnect the M16 ECU connector.
   Fig 1: Identifying Roof Console Box & Mayday ECU Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the O2 roof console box connector.
3. Measure the resistance of the wire harness side connectors.

   Standard resistance

   Tester Connection	Specified Condition
   M16-5 (SIG1) - O2-13 (SIG1)	Below 1 Ω
   M16-12 (SIG-) - O2-3 (SIG-)	Below 1 Ω
   M16-5 (SIG1) or O2-13 (SIG1) - Body ground	10 kΩ or higher
   M16-12 (SIG-) or O2-3 (SIG-) - Body ground	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the roof console box assembly.
   Fig 2: Identifying Map Light Plate Assembly Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance of the switch when each switch is pressed.

   Standard resistance

   Tester Connection	Switch Condition	Specified Condition
   13 (SIG1) - 3 (SIG-)	EMERGENCY	305 to 313 Ω
   13 (SIG1) - 3 (SIG-)	VOL+	812 to 831 Ω
   13 (SIG1) - 3 (SIG-)	VOL-	1811 to 1848 Ω

   NOTE:

   If replacement of the ECU is necessary, replace the mayday battery (backup battery) together with the ECU. After the replacement, register the ECU. Refer to REGISTRATION .

NG → See step   3 

OK → See step   4