DTC B1297 Clearance Sonar ECU Communication Stop

DESCRIPTION

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

DTC No.	DTC Detection Condition	Trouble Area
B1297	Clearance warning ECU communication stops	Clearance warning ECU Wire harness

Dtc B1297 Clearance Sonar Ecu Communication Stop. MULTIPLEX COMMUNICATION. Lexus IS250 IS220d GSE20 ALE20

When "+B of GND short malfunction of communication bus" DTCs (B1266 and B1267) are detected at the same time as "communication stop" DTC B1297, repair the "+B or GND short malfunction of communication bus" DTCs first.

1.INSPECT FUSE (LH-IG)

Remove the LH-IG fuse from the main body ECU LH (cowl side J/B LH).

Measure the resistance of the fuse.

REPLACE FUSE

OK

2.CHECK WIRE HARNESS (CLEARANCE WARNING ECU - BATTERY AND BODY GROUND)

Disconnect the Q37 ECU connector.

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

Standard voltage:
Tester Connection Condition Specified Condition
IG (Q37-8) - Body ground Engine switch on (IG) 10 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.CHECK RESISTANCE OF COMMUNICATION LINE

Disconnect the Q37, A27, J58 and J34 ECU connectors.

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

Standard resistance:
with Adaptive Front-Lighting System:
Tester Connection Specified Condition
M+ (Q37-26) - MPX2 (A27-6) Below 1 Ω
M+ (Q37-26) - Body ground 10 kΩ or higher
without Adaptive Front-Lighting System;
Tester Connection Specified Condition
M+ (Q37-26) - MPX- (J58-31) Below 1 Ω
M+ (Q37-26) - Body ground 10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE CLEARANCE WARNING ECU

Tester Connection	Condition	Specified Condition
IG (Q37-8) - Body ground	Engine switch on (IG)	10 to 14 V

Tester Connection	Specified Condition
E (Q37-27) - Body ground	Below 1 Ω