ABS works frequently but the brake is not effective or TCS operates frequently

1. ABS works frequently but the brake is not effective or TCS operates frequently description of symptom

ABS works frequently but the brake is not effective or TCS operates frequently.

2. ABS works frequently but the brake is not effective or TCS operates frequently 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. Diagnosis when the scan tool is not used

1) Tire inspection

Always inspect the size, air pressure, and uneven wear of the installed tires.

If the inspection results are normal, go to Brake distribution inspection on front and rear of vehicle.

If the inspection results are abnormal, replace the tire. After completing the procedure, go to Repair verification.

2) Inspection of brake distribution to the front and rear of the vehicle

Inspect the brake distribution to the front and rear of the vehicle.

If the inspection results are normal, go to Axle and related parts inspection.

If the inspection results are abnormal, repair the applicable brake system. After completing the procedure, go to Repair verification.

3) Axle and related parts inspection

Inspect the installation status of the axle and related parts.

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

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

4) 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.

5) 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 the applicable parts. After completing the procedure, go to Repair verification.

6) 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.

7) 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.

8) Repair verification

Check whether all the components are properly installed.

Perform a test drive and check the symptoms.

4. Diagnosis when using a scan tool

1) Wheel speed sensor output inspection

Turn OFF the ignition switch.

Connect the scan tool.

Observe the wheel speed of each wheel with a scan tool.

Check whether the lowest speed of all the wheels is 4 km/h {2.5 mph} or less and stable.

Note

Because different wheel speed readings may be displayed in the case of vehicles equipped with tires of different diameters on the front and rear wheels, check the speed after driving the vehicle at a fixed speed for a short period of time.

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

2) 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.

3) 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.

4) Repair verification

Check whether all the components are properly installed.

Perform a test drive and check the symptoms.