Toyota Yaris: Vehicle Stability Control System / Brake System Control Module "A" System Voltage System Voltage High (C137BA3)

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 High (C137BA3)

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 deviates 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
C137BA3	Brake System Control Module "A" System Voltage System Voltage High	The +BS terminal voltage is 17.4 V or more for 0.8 seconds or more.	Auxiliary battery Charging system Wire harness and connector Skid control ECU (brake actuator assembly)	Brake

WIRING DIAGRAM

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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".
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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

CHECK OR REPLACE CHARGING SYSTEM OR AUXILIARY BATTERY

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))

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
A108-38 (+BS) - A108-25 (GND1)	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

(d) Turn the ignition switch off.

4.	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

Result	Proceed to
C137BA3 is not output	A
C137BA3 is output	B

USE SIMULATION METHOD TO CHECK

REPLACE BRAKE ACTUATOR ASSEMBLY

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