ECU Power Source Circuit: Procedure

1. Remove the MAYDAY and AM2 fuses from the engine room junction block.
2. Remove the ACC and GAUGE fuses from the driver side junction block.
3. Measure the resistance of the fuses.

   Standard resistance

   Below 1 Ω

NG → REPLACE FUSE 

OK: Go to next step 

1. Remove the ACC CUT relay from the engine room relay block.
   Fig 1: Identifying ACC CUT Relay Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance of the relay.

   Standard resistance

   Tester connection	Specified Condition
   3 - 4	Below 1 Ω
   3 - 4	10 kΩ or higher (when battery voltage is applied to terminals 1 and 2)

NG → REPLACE RELAY 

OK: Go to next step 

1. Disconnect the M15 ECU connector.
   Fig 2: Identifying Mayday ECU Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage and resistance of the wire harness side connector.

   Standard voltage

   Tester Connection	Condition	Specified Condition
   M15-1 (+B) - Body ground	Always	10 to 14 V
   M15-13 (IG) - Body ground	Ignition switch ON	10 to 14 V
   M15-14 (ACC) - Body ground	Ignition switch ACC	10 to 14 V

   Standard resistance

   Tester Connection	Specified Condition
   M15-12 (E) - Body ground	Below 1 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 → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   4