Toyota Yaris: Vehicle Stability Control System / Brake System Control Module "A" System Voltage System Voltage Low (C137BA2)

Toyota Yaris XP210 (2020-2025) Reapir and Service Manual / Brake / Brake Control / Dynamic Control Systems / Vehicle Stability Control System / Brake System Control Module "A" System Voltage System Voltage Low (C137BA2)

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 ABS operation.

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 auxiliary 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

DTC Output from

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.
  • Auxiliary battery
  • Charging system
  • Wire harness and connector
  • Skid control ECU (brake actuator assembly)

Brake

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • After replacing the skid control ECU (brake actuator assembly), perform "Calibration".

    Click here

PROCEDURE

1.

CHECK AUXILIARY BATTERY

(a) Check the auxiliary battery voltage.

Standard Voltage:

Tester Connection

Condition

Specified Condition

Positive (+) auxiliary battery terminal - Negative (-) auxiliary battery terminal

Always

11 to 14 V
NG

CHECK OR REPLACE CHARGING SYSTEM OR AUXILIARY BATTERY

OK

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.

(b) Disconnect the A108 skid control ECU (brake actuator assembly) connector.

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Actuator Assembly))

(c) Check both the connector case and the terminals for deformation and corrosion.

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

A108-38 (+BS) - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (+BS CIRCUIT)
OK

3.

CHECK HARNESS AND CONNECTOR (IGR TERMINAL)

(a) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A108-12 (IGR) - Body ground

Ignition switch ON

10.5 to 16 V

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Actuator Assembly))
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

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

A108-25 (GND1) - Body ground

1 minute or more after disconnecting the cable from the negative (-) auxiliary battery terminal

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

CLEAR DTC

(a) Reconnect the A108 skid control ECU (brake actuator assembly) connector.

(b) Operate the GTS to clear the codes.

Chassis > Brake > Clear DTCs

(c) Press the DTC clear button.

(d) Turn the ignition switch off.

NEXT

6.

RECONFIRM DTC

(a) Based on the Freeze Frame Data and interview with the customer, attempt to reproduce the conditions when the malfunction occurred.

(b) Operate the GTS to read the DTCs.

Chassis > Brake > Trouble Codes

(c) Check if the same DTC is output.

Result

Proceed to

C137BA2 is not output

A

C137BA2 is output

B
A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE ACTUATOR ASSEMBLY

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