Dtc B1296 Front Light Ecu Communication Stop

Communication System. Lexus Gs430, Gs300. Uzs190 Grs190
Multiplex Communication. Lexus Gs430, Gs300. Uzs190 Grs190

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK OPERATION

INSPECT FUSE (MPX-B, D/C CUT)

CHECK WIRE HARNESS (ENGINE ROOM NO.2 R/B (FRONT CONTROLLER) - BATTERY AND BODY GROUND)

CHECK RESISTANCE OF COMMUNICATION LINE

CHECK OPERATION OF FRONT CONTROLLER

DTC B1296 Front Light ECU Communication Stop


DESCRIPTION

This DTC is detected when communication between the engine room No. 2 junction block (front controller) and gateway ECU stops for more than 10 seconds.

DTC No.
DTC Detection Condition
Trouble Area
B1296
Front controller communication stops
  1. Engine room No. 2 junction block (front controller)
  2. Wire harness

WIRING DIAGRAM


Lexus Gs430, Gs300. Uzs190 Grs190.Multiplex Communication.Multiplex Communication System. Dtc B1296 Front Light Ecu Communication Stop


INSPECTION PROCEDURE

1.CHECK OPERATION

  1. Turn the headlight dimmer switch ON and check that the headlights illuminate.

    OK:
    Headlights illuminate.


NG
Go to step 2
OK

REPLACE ENGINE ROOM NO. 2 RELAY BLOCK (FRONT CONTROLLER)

2.INSPECT FUSE (MPX-B, D/C CUT)

  1. Remove the MPX-B and D/C CUT fuses from the engine room No. 1 relay block, junction block.

  1. Measure the resistance of the fuses.

    Standard resistance:
    Below 1 Ω


NG
REPLACE FUSE
OK


3.CHECK WIRE HARNESS (ENGINE ROOM NO.2 R/B (FRONT CONTROLLER) - BATTERY AND BODY GROUND)

Lexus Gs430, Gs300. Uzs190 Grs190.Multiplex Communication.Multiplex Communication System. Dtc B1296 Front Light Ecu Communication Stop

  1. Disconnect the 2F and 2E relay block controllers from the engine room No. 2 relay block, junction block.

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

    Standard voltage:
    Tester Connection
    		Specified Condition
    2E-4 (FMB3) - Body ground
    		10 to 14 V
    Standard resistance:
    Tester Connection
    		Specified Condition
    2F-1 (E) - Body ground
    		Below 1 Ω


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK


4.CHECK RESISTANCE OF COMMUNICATION LINE

Lexus Gs430, Gs300. Uzs190 Grs190.Multiplex Communication.Multiplex Communication System. Dtc B1296 Front Light Ecu Communication Stop

  1. Disconnect the L22 switch connector.

  1. Disconnect the A32 or A31 ECU connector.

  1. Disconnect the 2F controller from the engine room relay block No. 2.

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

    Standard resistance:
    Tester Connection
    		Specified Condition
    2F-5 (MPX1) - L22-7 (MPX2)
    		Below 1 Ω
    2F-6 (MPX2) - A32-6 (MPX4)
    		Below 1 Ω
    2F-6 (MPX2) - A31-6 (MPX1)
    		Below 1 Ω
    Result:
    Result
    		Proceed to
    All are OK
    		A
    One or two is / are OK
    		B
    All are NG
    		C


B
REPLACE ENGINE ROOM NO. 2 RELAY BLOCK AND HARNESS AND CONNECTOR

C
REPAIR OR REPLACE HARNESS AND CONNECTOR
A


5.CHECK OPERATION OF FRONT CONTROLLER

  1. After replacing the front controller with a normally functioning controller, check that the headlights illuminate.

    OK:
    Headlights illuminate.


NG
REPLACE ENGINE ROOM NO. 2 RELAY BLOCK
OK

REPLACE FRONT CONTROLLER