DTC C1203: ECM Communication Circuit [06/2018 - ]: Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2024 Lexus ES 300h, 2023 Lexus ES 300h, 2022 Lexus ES 300h, 2021 Lexus ES 300h, and 2020 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	MIL	Note
C1203	ECM Communication Circuit	1161	Either of the following is detected: Identification information sent from other ECUs does not match with the value stored when shipped from the factory. Identification information sent from other ECUs is not stored when shipped from the factory.	Other ECUs are not installed correctly Skid control ECU (brake booster with master cylinder assembly)	Comes on	INF Code 1161: SAE Code C124A Electronically controlled brake system DTC HINT: DTC C1203 (INF code 1161) is cleared when the conditions return to normal. This DTC is stored when incorrect identification information is detected and is not due to an ECM communication error.

DTC No.

Detection Item

INF Code

DTC Detection Condition

Trouble Area

MIL

Note

C1203

ECM Communication Circuit

1161

Either of the following is detected:

Identification information sent from other ECUs does not match with the value stored when shipped from the factory.
Identification information sent from other ECUs is not stored when shipped from the factory.

Other ECUs are not installed correctly
Skid control ECU (brake booster with master cylinder assembly)

Comes on

INF Code 1161: SAE Code C124A
Electronically controlled brake system DTC

HINT:

DTC C1203 (INF code 1161) is cleared when the conditions return to normal.
This DTC is stored when incorrect identification information is detected and is not due to an ECM communication error.

NOTE:

DTC C1203 is output when an incorrect ECU is installed. If initialization is performed and learning occurs with an incorrect ECU installed, operations and functions will differ from those stored when the vehicle was shipped from the factory. Therefore, make sure that learning occurs properly.