DTC B1272 Power Seat ECU Communication Stop

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	Position control ECU and switch (driver seat ECU) Wire harness

Dtc B1272 Power Seat Ecu Communication Stop. MULTIPLEX COMMUNICATION. Lexus IS250 IS220d GSE20 ALE20

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)

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

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

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

Measure the resistance of the fuses.

REPLACE FUSE

OK

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

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

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

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

*1: LHD

*2: RHD

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

*1: LHD

*2: RHD

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.CHECK RESISTANCE OF COMMUNICATION LINE

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

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

Dtc B1272 Power Seat Ecu Communication Stop. MULTIPLEX COMMUNICATION. Lexus IS250 IS220d GSE20 ALE20

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) - MPX1 (P33-27) Below 1 Ω

*1: LHD

*2: RHD

REPAIR OR REPLACE HARNESS OR CONNECTOR AND REPLACE POSITION CONTROL ECU

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE POSITION CONTROL ECU AND SWITCH

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