brake operation sounds are heard from the hydraulic unit even though the brake is not applied

1. Brake operation sounds are heard from the hydraulic unit even though the brake is not applied description of symptom

The operation sound of the hydraulic unit can be heard even though the brake pedal is not depressed.

2. Brake operation sounds are heard from the hydraulic unit even though the brake is not applied diagnostics

1. Preliminary inspection

Perform the brake control system inspection.

Refer to "54.Brake Control 4A.Troubleshooting(ABS/ESC) diagnostic System Check - Brake Controls".

Inspect for the following.

There should be no malfunctions in the warning light and indicator light operation.
There should be no DTC input.

2. Visual inspection

Visually inspect the vehicle condition with the following in mind before installing, removing, disassembling, and inspecting the components.

Terminal connection status inspection
Inspection for aftermarket accessory power diverged from the EHCU
EHCU ground installation status inspection
Installation status inspection of the pipes and hoses in the brake system

3. Diagnostics

1) Condition check upon generation of operating sound

It is normal if it operates under the following conditions.

At first driving after the engine is started.
The vehicle speed is 10 km/h {6.2 mph} or less.
At shift-down or clutch operation
When the vehicle is running on slippery (frozen or snow-covered) roads or under rough road conditions
When turning at high speed
When passing over a protrusion such as a curb

2) Wheel speed sensor installation status inspection

Inspect the installation status of the wheel speed sensors.

If the installation is normal, go to Wheel speed sensor and exciter ring inspection.

If the installation is abnormal, repair the installation condition of the wheel speed sensor. After completing the procedure, go to Repair verification.

3) Wheel speed sensor and exciter ring inspection

Inspect for foreign material attached to the wheel speed sensor or exciter ring.

If the inspection results are normal, go to Wheel speed sensor circuit inspection.

If the inspection results are abnormal, repair or replace the applicable parts. After completing the procedure, go to Repair verification.

4) Wheel speed sensor circuit inspection

Refer to DTCs C0031[01] - C003A[2F], and inspect the wheel speed sensor circuit.

If the inspection results are normal, go to EHCU replacement.

If the inspection results are abnormal, repair the wheel speed sensor. After completing the procedure, go to Repair verification.

5) EHCU replacement

Note

Perform programming after replacing the EHCU.

Refer to "4.Brakes 4Z.Brake Electrical Control EHCU removal".

Refer to "4.Brakes 4Z.Brake Electrical Control EHCU installation".

Refer to "4.Brakes 4Z.Brake Electrical Control EHCU setting".

After completing the procedure, go to Repair verification.

6) Repair verification

Check whether all the components are properly installed.

Perform a test drive and check the symptoms.