DTC C137B-A2: Brake System Control Module "A" System Voltage System Voltage Low [11/2023 - ]: Description

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If a malfunction is detected in the power supply circuit, the No. 2 skid control ECU (brake actuator assembly) stores this DTC and the fail-safe function prohibits operation of ABS, brake assist, regenerative brake cooperative control, etc.

This DTC is stored when the +BS, IG1 or IG2 terminal voltage meets one of the DTC detection conditions due to a malfunction in the power supply or charging circuit such as the auxiliary battery or DC/DC converter circuit, etc.

This DTC is cleared when the voltage at terminal +BS, IG1 and IG2 returns to normal.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Note
C137B-A2	Brake System Control Module "A" System Voltage System Voltage Low	Any of the following is detected: When the voltage at terminal +BS is less than 8.5 V, the master cylinder pressure sensor is invalid for 10 seconds or more. When the voltage at terminal +BS is less than 8.5 V, the brake pedal stroke sensor assembly is invalid for 10 seconds or more. When the voltage at terminal +BS is less than 8.5 V, the wheel cylinder pressure sensor is invalid for 10 seconds or more. When the +BS terminal voltage is below 9.5 V, the power source voltage for all speed sensors is continuously low for 60 seconds or more. When the vehicle speed is 3 km/h (2 mph) or more, the voltage at terminal IG1 or terminal IG2 is excessively low for 10 seconds or more. When the +BS terminal voltage is below 9.5 V and the solenoid relay is ON, the relay contact is OFF continuously for 1.22 seconds or more. When the +BS terminal voltage is below 9.5 V, motor fail-safe relay overcurrent continues for 1.05 seconds or more.	Wire harness and connector No. 2 skid control ECU (brake actuator assembly)	Comes on	SAE Code: C137C Output ECU: No. 2 skid control ECU (brake actuator assembly)