BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for Gasoline Model without Electric Parking Brake System TMC Made): C137BA2; Brake System Control Module "A" System Voltage System Voltage Low; 2023 - 2026 MY Corolla Corolla Hatchback GR Corolla [09/2022

Last Modified: 08-23-2025	6.11:8.1.0	Doc ID: RM10000000260S6
Model Year Start: 2023	Model: GR Corolla	Prod Date Range: [09/2022 - ]
Title: BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for Gasoline Model without Electric Parking Brake System TMC Made): C137BA2; Brake System Control Module "A" System Voltage System Voltage Low; 2023 - 2026 MY Corolla Corolla Hatchback GR Corolla [09/2022 - ]

DTC

C137BA2

Brake System Control Module "A" System Voltage System Voltage Low

DESCRIPTION

If a malfunction is detected in the power supply circuit, the skid control ECU (brake actuator assembly) stores this DTC and the fail-safe function prohibits operation of ABS, brake assist, etc.

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

The DTC is cleared when the +BS terminal voltage returns to normal.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
C137BA2	Brake System Control Module "A" System Voltage System Voltage Low	Any of the following is detected: 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. After the +BS terminal voltage is below 9.5 V continuously for 3 seconds or more, the +BS terminal voltage is below 9.5 V continuously for 7 seconds or more at a vehicle speed exceeding 3 km/h (2 mph). When the +BS terminal voltage is 9.5 V or higher and the vehicle speed exceeds 15 km/h (9 mph), the IGR terminal voltage is 10 V or less continuously for 60 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 Skid control ECU (brake actuator assembly)

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.
Before performing troubleshooting, make sure to confirm that the battery voltage is normal.
Click here

PROCEDURE

1.	CHECK FREEZE FRAME DATA (+BS VOLTAGE AND +BM VOLTAGE)

(a) Using the GTS, check for Freeze Frame Data that is recorded when DTC C137BA2 is stored.

Chassis > Brake/EPB

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

+BS Voltage

+BS terminal voltage value (value detected by ECU)

Min.: 0.0 V

Max.: 25.5 V

Ignition switch ON: 11.0 to 14.0 V

Changes in proportion to battery voltage

HINT:

This is the voltage detected at terminal +BS (which supplies power to each solenoid) of the skid control ECU (brake actuator assembly)

+BM Voltage

BM terminal voltage value (value detected by ECU)

Min.: 0.0 V

Max.: 25.5 V

Ignition switch ON: 11.0 to 14.0 V

Changes in proportion to battery voltage

HINT:

This is the voltage detected at terminal BM (which supplies power to the ABS motor) of the skid control ECU (brake actuator assembly)

Chassis > Brake/EPB > DTC(C137BA2) > Freeze Frame Data

Tester Display
+BS Voltage
+BM Voltage

Result	Proceed to
+BS Voltage and +BM Voltage are less than 9.5 V.	A
Only +BS Voltage is less than 9.5 V.	B
Only +BM Voltage is less than 9.5 V, or both +BS Voltage and +BM Voltage are 9.5 V or more.	C

CHECK OR REPLACE CHARGING SYSTEM COMPONENT OR BATTERY

REPLACE BRAKE ACTUATOR ASSEMBLY

2.	CHECK HARNESS AND CONNECTOR (+BS TERMINAL)

(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

OK:

The connector is securely connected.

*a	Front view of wire harness connector (to Skid Control ECU (Brake Actuator Assembly))

(b) Disconnect the A140 skid control ECU (brake actuator assembly) connector.

OK:

No deformation or corrosion.

(d) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Condition	Specified Condition
A140-14 (+BS) - Body ground	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	CHECK HARNESS AND CONNECTOR (IGR TERMINAL)

(a) Turn the ignition switch to ON.

*a	Front view of wire harness connector (to Skid Control ECU (Brake Actuator Assembly))

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Condition	Specified Condition
A140-45 (IGR) - Body ground	Ignition switch ON	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	CHECK HARNESS AND CONNECTOR (GND1 TERMINAL)

(a) Turn the ignition switch off.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
A140-1 (GND1) - Body ground	1 minute or more after disconnecting the cable from the negative (-) battery terminal	Below 1 Ω

REPLACE BRAKE ACTUATOR ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR