Dtc B1271 Combination Meter Ecu Communication Stop

Communication System. Lexus Is250, Is220D. Gse20 Ale20
Multiplex Communication. Lexus Is250, Is220D. Gse20 Ale20

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

INSPECT FUSE (DOME, MPX-B)

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

CHECK RESISTANCE OF COMMUNICATION LINE

DTC B1271 Combination Meter ECU Communication Stop


DESCRIPTION

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

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

WIRING DIAGRAM


Lexus Is250, Is220D. Gse20 Ale20.Multiplex Communication.Multiplex Communication System. Dtc B1271 Combination Meter Ecu Communication Stop


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.INSPECT FUSE (DOME, MPX-B)

  1. Remove the DOME and MPX-B fuses from the engine room J/B No. 1.

  1. Measure the resistance of the fuses.

    Standard resistance:
    Below 1 Ω


NG
REPLACE FUSE
OK


Go to step 3

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


    Lexus Is250, Is220D. Gse20 Ale20.Multiplex Communication.Multiplex Communication System. Dtc B1271 Combination Meter Ecu Communication Stop

  1. Disconnect the J34 ECU connector.

  1. Measure the voltage and resistance of the wire harness side connector.

    Standard voltage:
    Tester Connection
    		Condition
    		Specified Condition
    B (J34-23) - Body ground
    		Always
    		10 to 14 V
    B (J34-24) - Body ground
    		Always
    		10 to 14 V
    Standard resistance:
    Tester Connection
    		Specified Condition
    E2 (J34-1) - Body ground
    		Below 1 Ω
    ES (J34-13) - Body ground
    		Below 1 Ω


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3.CHECK RESISTANCE OF COMMUNICATION LINE


    Lexus Is250, Is220D. Gse20 Ale20.Multiplex Communication.Multiplex Communication System. Dtc B1271 Combination Meter Ecu Communication Stop

  1. Disconnect the J34, J76, A27 and J58 ECU connectors.

  1. Measure the resistance between the specified terminals on the wire harness side connectors.

    Standard resistance:
    Tester Connection
    		Specified Condition
    MPX- (J34-18) - MPI1 (J76-4)
    		Below 1 Ω
    *1MPX+ (J34-6) - MPX2 (A27-6)
    		Below 1 Ω
    *2MPX+ (J34-6) - MPX- (J58-31)
    		Below 1 Ω
    HINT:
    1. *1: w/ Adaptive front-lighting system
    2. *2: w/o Adaptive front-lighting system
    Result:
    Result
    		Proceed to
    Both are OK
    		A
    One is OK
    		B
    Both are NG
    		C


B
REPLACE COMBINATION METER ECU AND REPAIR OR REPLACE HARNESS OR CONNECTOR

C
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE COMBINATION METER ECU