DTC    B1271    Combination Meter ECU Communication Stop

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DESCRIPTION

This DTC is detected when communication between the combination meter assembly (meter ECU) and multiplex network gateway ECU stops for more than 10 seconds.

DTC No.
DTC Detection Condition
Trouble Area
B1271
Combination meter assembly communication stops
  1. Combination meter assembly (meter ECU)
  2. Wire harness

WIRING DIAGRAM


B110980E03


INSPECTION PROCEDURE

HINT:
When "+B of 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


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.

  1. Measure the resistance of the fuses.

    Standard resistance:
    Below 1 Ω



NG
REPLACE FUSE
OK


3.CHECK WIRE HARNESS (COMBINATION METER - BATTERY AND BODY GROUND)


    B111024E01

  1. Disconnect the C8 and C9 meter connectors.

  1. Measure the voltage of the wire harness side connectors.

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

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

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



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


4.CHECK RESISTANCE OF COMMUNICATION LINE

  1. Disconnect the A24 and G1 ECU connectors (w/ LEXUS navigation system).



  1. Disconnect the A24 and C4 ECU connectors (w/o LEXUS navigation system).


    B111055E03

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

    Standard resistance:
    Tester Condition
    		Specified Condition
    C9-4 (MPX+) - A24-24 (MPX1)
    		Below 1 Ω
    C8-5 (MPX-) - C4-12 (MPX-) (*2)
    		Below 1 Ω
    C8-5 (MPX-) - G1-13 (MPI2) (*1)
    		Below 1 Ω

    *1: w/ LEXUS Navigation System
    *2: w/o LEXUS Navigation System



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE COMBINATION METER