Back-up Power Source Circuit: Procedure

1. Remove the ECU-B NO. 2 fuse from the engine room relay block.
2. Measure the resistance of the fuse.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   ECU-B NO. 2 fuse	Always	Below 1 Ω

NG → REPLACE FUSE 

OK: Go to next step 

1. Install the ECU-B NO. 2 fuse.
   Fig 1: Identifying Harness And Connector (Air Conditioning Amplifier - Battery)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the D37 and D38 amplifier connectors.
3. Measure the voltage according to the value(s) in the table below.

   Standard voltage

   Tester Connection	Condition	Specified Condition
   D37-21 (B) - Body ground	Always	11 to 14 V
   D38-24 (+B2) - Body ground	Always	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Measure the resistance according to the value(s) in the table below.
   Fig 2: Identifying Harness And Connector (Air Conditioning Amplifier - Body Ground)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard resistance

   Tester Connection	Condition	Specified Condition
   D37-14 (GND) - Body ground	Always	Below 1 Ω
   D38-20 (GND2) - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   4