Toyota Corolla Cross Owners & Service Manuals

Toyota Corolla Cross: Electronic Brake Booster Control Module "A" System Internal Failure (C121F04,C14C9A3)

Toyota Corolla Cross (2022-2024) Service Manual / Brake / Brake Control / Dynamic Control Systems / Electronically Controlled Brake System (for Hev Model) / Electronic Brake Booster Control Module "A" System Internal Failure (C121F04,C14C9A3)

DESCRIPTION

If there is a malfunction in the power source circuit, the electric brake booster (brake booster with master cylinder assembly) stores a DTC, and ABS, brake assist, regenerative braking, etc. operation is prohibited by fail-safe control.

When a malfunction in the auxiliary battery, charging circuit, etc. results in a voltage differential between the +BS terminal and the internal circuit terminal of the electric brake booster (brake booster with master cylinder assembly), this DTC is stored.

When the voltage between the +BS terminal and the internal circuit terminal of the electric brake booster (brake booster with master cylinder assembly) returns to normal, this DTC is cleared.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

DTC Output from

Note

C121F04

Electronic Brake Booster Control Module "A" System Internal Failure

A voltage difference of 1.0 V or more is detected between the +BS terminal and the IGR terminal, and the voltage of the IGR terminal is 3.2 V or less.

  • Wire harness or connector
  • Electric brake booster (brake booster with master cylinder assembly)

Comes on

Brake Booster

  • SAE Code: C121F (Case 2 to 11)
  • Output ECU: Electric brake booster (brake booster with master cylinder assembly)

C14C9A3

Electronic Brake Booster Control Module "A" System Voltage High

The +BS terminal voltage is less than 27.5 V for 0.2 seconds or more.

  • Wire harness or connector
  • Electric brake booster (brake booster with master cylinder assembly)

Comes on

Brake Booster

  • SAE Code: C14CB
  • Output ECU: Electric brake booster (brake booster with master cylinder assembly)

MONITOR DESCRIPTION

C121F (Case 2 to 9):
  • When the electronically controlled brake system is starting, operating or shutting down and an ECU internal malfunction is detected, the electric brake booster (brake booster with master cylinder assembly) illuminates the MIL and stores this DTC.
C121F (Case 10):
  • When the electronically controlled brake system is operating or shutting down, the motor is not operating, the supply voltage of the electric brake booster (brake booster with master cylinder assembly) exceeds a certain value and the difference between the supply voltage of the electric brake booster (brake booster with master cylinder assembly) and the voltage of the motor drive circuit exceeds a certain value, the electric brake booster (brake booster with master cylinder assembly) illuminates the MIL and stores this DTC.
C121F (Case 11):
  • When the electronically controlled brake system is operating or shutting down, the motor is not operating, the motor drive circuit voltage is less than a certain value, and the difference between the supply voltage of the electric brake booster (brake booster with master cylinder assembly) and voltage of the motor drive circuit exceeds a certain value, the electric brake booster (brake booster with master cylinder assembly) illuminates the MIL and stores this DTC.
C14CB:
  • When the electronically controlled brake system is operating and the power supply voltage of the electric brake booster (brake booster with master cylinder assembly) exceeds a certain value, the electric brake booster (brake booster with master cylinder assembly) illuminates the MIL and stores this DTC.

MONITOR STRATEGY

Related DTCs

C121F (Case 2 to 9): ECU internal monitoring (brake booster with master cylinder assembly)

C121F (Case 10): Booster supply voltage / motor drive circuit voltage divider monitor

C121F (Case 11): Motor drive circuit supply circuit monitor

C14CB: UBB voltage monitoring (over voltage shutdown level)

Required Sensors/Components(Main)

Electric brake booster (brake booster with master cylinder assembly)

Required Sensors/Components(Related)

Electric brake booster (brake booster with master cylinder assembly)

Frequency of Operation

Continuous

Duration

-: C121F (Case 2 and 9)

Immediately up to 0.08 seconds: C121F (Case 3 and 8)

0.01 seconds: C121F (Case 11)

0.01 to 0.084 seconds: C121F (Case 4)

0.06 seconds: C121F (Case 6 and 7)

0.12 seconds: C121F (Case 5)

0.2 seconds: C121F (Case 10) and C14CB

MIL Operation

Immediately: C121F (Case 2 to 11)

2 driving cycles: C14CB

Sequence of Operation

None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored

TMC's intellectual property

Other conditions belong to TMC's intellectual property

-

TYPICAL MALFUNCTION THRESHOLDS

TMC's intellectual property

-

COMPONENT OPERATING RANGE

TMC's intellectual property

-

CONFIRMATION DRIVING PATTERN

NOTICE:

When performing the normal judgment procedure, make sure that the driver door is closed and is not opened at any time during the procedure.

HINT:

  • After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
  • When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.
  1. Connect the GTS to the DLC3.
  2. Turn the ignition switch to ON and turn the GTS on.
  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
  4. Turn the ignition switch off.
  5. Turn the ignition switch to ON (READY) and turn the GTS on.
  6. Wait for 1 second or more. [*]

    HINT:

    [*]: Normal judgment procedure.

    The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.

  7. Enter the following menus: Chassis / Brake Booster / Utility / All Readiness.
  8. Check the DTC judgment result.

    HINT:

    • If the judgment result shows NORMAL, the system is normal.
    • If the judgment result shows ABNORMAL, the system has a malfunction.
    • If the judgment result shows INCOMPLETE, perform driving pattern again.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

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 Electric Brake Booster (Brake Booster with Master Cylinder Assembly))

(b) Disconnect the A189 electric brake booster (brake booster with master cylinder assembly) connector.

(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

A189-11 (+BS) - Body ground

Always

11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

2.

CHECK HARNESS AND CONNECTOR (IGR 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 Electric Brake Booster (Brake Booster with Master Cylinder Assembly))

(b) Disconnect the A189 electric brake booster (brake booster with master cylinder assembly) connector.

(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

A189-4 (IGR) - Body ground

Ignition switch ON

11 to 14 V

OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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