DTC C1311: Open Circuit in Main Relay 1; DTC C1312: Short Circuit in Main Relay 1 [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.

The main relay supplies power to the switching solenoid and the linear solenoid.

The main relay remains on for approximately 2 minutes after the power switch is turned off and the input of brake pedal operation signals stops, and supplies power to the system to keep it ready to operate.

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	MIL	Note
C1311	Open Circuit in Main Relay 1	1	Either of the following is detected: When the power switch is on (READY): The BS terminal voltage is less than 3.5 V for 0.05 seconds or more, when the IG1 terminal voltage is 9.5 V or more and operation of the main relay is requested. When the power switch is off: The BS terminal voltage is less than 3.5 V for 0.05 seconds or more, when operation of the main relay is requested.	Open or short in main relay circuit Skid control ECU (brake booster with master cylinder assembly)	Comes on	INF Code 1: SAE Code C12FA Electronically controlled brake system DTC
C1312	Short Circuit in Main Relay 1	2	The BS terminal voltage is 3.5 V or more for 4.5 seconds or more, when operation of the main relay is requested.	Short in main relay circuit Main relay internal stuck Skid control ECU (brake booster with master cylinder assembly)	Comes on	INF Code 2: SAE Code C12FB Electronically controlled brake system DTC