Inspection Procedure

HINT:

When "+B or GND short malfunction of communication bus" DTCs (B1266 and B1267) are detected at the same time as "communication stop" DTC B1271, repair the "+B or GND short malfunction of communication bus" DTCs first.

1. CHECK OPERATION 
   1. Check that the tachometer can operate properly while the engine is idling.

      HINT:

      With this inspection, the combination meter CPU can be diagnosed if it works normally or not.

      OK: Tachometer operates properly while engine is idling. 

   OK: Go to step  4

   NG: Go to next step. 

2. INSPECT FUSE (ECU-B NO. 1, DOME) 
   1. Remove the ECU-B No. 1 and DOME fuses from the fusible link block and instrument panel junction block.
   2. Measure the resistance of the fuses.

      Standard resistance: 

      Below 1 Ω 

   NG: REPLACE FUSE 

   OK: Go to next step. 

3. CHECK HARNESS AND CONNECTOR (COMBINATION METER - BATTERY AND BODY GROUND) 
   1. Disconnect the C8 and C9 meter connectors.
   2. Measure the voltage of the wire harness side connectors.

      Standard voltage 

      TESTER CONNECTION SPECIFIED CONDITION CHART
      
      

      Tester Connection	Specified Condition
      C8-15 (B) - Body ground	10 to 14 V
      C8-16 (B) - Body ground	10 to 14 V

   3. Measure the resistance of the wire harness side connectors.

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART
      
      

      Tester Connection	Specified Condition
      C9-1 (E) - Body ground	Below 1 Ω

   Fig 1: Identifying Terminals Of C8 And C9 Meter Connectors
   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

   OK: Go to next step. 

4. CHECK RESISTANCE OF COMMUNICATION LINE 
   1. Disconnect the A20 and G3 ECU connectors (with LEXUS navigation system).
   2. Disconnect the A20 and C4 ECU connectors (without LEXUS navigation system).
      Fig 2: Identifying Terminals Of A20, C4 And G3 ECU Connectors

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   3. Measure the resistance of the wire harness side connectors.

      Standard resistance 

      CONNECTOR TERMINALS REFERENCE
      
      

      Tester Condition	Specified Condition
      C9-4 (MPX+) - A20-24 (MPX1)	Below 1 Ω
      C8-5 (MPX-) - C4-12 (MPX-) ((1))	Below 1 Ω
      C8-5 (MPX-) - G3-13 (MPI2) ((2))	Below 1 Ω
      (1) with LEXUS Navigation System (2) without LEXUS Navigation System

   NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

   OK: REPLACE COMBINATION METER