Disconnect the gateway ECU connector.

Check for DTCs and note any codes that are output.

The LEXUS IS250 Multiplex Communication System (MPX) uses serial communication, which converts multiple pieces of information into serial communication data. As a result, they can be transmitted through a single communication wire.

Lexus IS250 IS220d GSE20 ALE20 MULTIPLEX COMMUNICATION

Lexus IS250 IS220d GSE20 ALE20 MULTIPLEX COMMUNICATION

Lexus IS250 IS220d GSE20 ALE20 MULTIPLEX COMMUNICATION

If some ECUs and sensors are not displayed on the "Communication Bus Check" screen of the intelligent tester and some ECUs and sensors repeatedly appear and disappear from the screen when the CAN main bus lines are normal (there is no open, short, short to B+, or short to GND in the main bus lines), there may be an open circuit in either of the CAN branch lines.

A short to GND is suspected the CAN bus line when the resistance between terminals 4 (CG) and 6 (CANH), or terminals 4 (CG) and 14 (CANL) of the DLC3 is below 1 kΩ.

A short to B+ is suspected in the CAN bus line when the resistance between terminals 6 (CANH) and 16 (BAT), or terminals 14 (CANL) and 16 (BAT) of the DLC3 is below 1 MΩ.

The CAN bus lines are considered to be shorted when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is below 54 Ω.