Lexus IS250 · Service Manual COMMUNICATION SYSTEM

B1272

Diagnostic trouble codes

DESCRIPTION

This DTC is detected when communication between the position control ECU and switch (driver seat ECU) and gateway ECU stops for more than 10 seconds.
DTC No.
 DTC Detection Condition
 Trouble Area
B1272
 Position control ECU and switch (driver seat ECU) communication stops
  1. Position control ECU and switch (driver seat ECU)
  2. Wire harness

WIRING DIAGRAM

B110902E03
B133426E01

INSPECTION PROCEDURE

HINT:
When "+B of GND short malfunction of communication bus" DTCs (B1214 and B1215) are detected at the same time as "communication stop" DTC B1272, repair the "+B or GND short malfunction of communication bus" DTCs first.


1. INSPECT FUSE (FR P/SEAT LH (LHD), FR P/SEAT RH (RHD), MPX-B)

  1. Remove the FR P/SEAT LH fuse from the main body ECU LH (cowl side J/B LH) (for LHD).

  1. Remove the FR P/SEAT RH fuse from the main body ECU RH (cowl side J/B RH) (for RHD).

  1. Remove the MPX-B fuse from the engine room J/B No. 1.

  1. Measure the resistance of the fuses.

    Standard resistance:
    Below 1 Ω



 NG
REPLACE FUSE
OK


2. CHECK WIRE HARNESS (POSITION CONTROL ECU AND SWITCH - BATTERY AND BODY GROUND)

  1. Disconnect the U6 and U7 ECU connectors (for LHD).

  1. B131014E02
    Disconnect the T6 and T7 ECU connectors (for RHD).

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    *1SYSB (U7-8) - Body ground
    *2SYSB (T7-8) - Body ground
    		 Always
    		 10 to 14 V
    *1+B (U6-5) - Body ground
    *2+B (T6-5) - Body ground
    		 Always
    		 10 to 14 V

    HINT:
    1. *1: LHD
    2. *2: RHD

    Standard resistance:
    Tester Connection
    		 Specified Condition
    *1GND (U6-1) - Body ground
    		 Below 1 Ω
    *2GND (T6-1) - Body ground
    		 Below 1 Ω

    HINT:
    1. *1: LHD
    2. *2: RHD



 NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3. CHECK RESISTANCE OF COMMUNICATION LINE

  1. Disconnect the U7, 2F and J55 ECU connectors (for LHD).

  1. Disconnect the T7, L17 and P33 ECU connectors (for RHD).B133469E01

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

    Standard resistance:
    Tester Connection
    		 Specified Condition
    *1MPX1 (U7-1) - 2F-5
    *2MPX1 (T7-1) - MPX1 (L17-7)
    		 Below 1 Ω
    *1MPX1 (U7-1) - MPX2 (J55-24)
    *2MPX1 (T7-1) - MPX2 (P33-27)
    		 Below 1 Ω

    HINT:
    1. *1: LHD
    2. *2: RHD

    Result:
    Result
    		 Proceed to
    Both are OK
    		 A
    One is OK
    		 B
    Both are NG
    		 C



B
REPAIR OR REPLACE HARNESS OR CONNECTOR AND REPLACE POSITION CONTROL ECU

C
REPAIR OR REPLACE HARNESS OR CONNECTOR
A

REPLACE POSITION CONTROL ECU AND SWITCH


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