HYDRAULIC BRAKE BOOSTER (HBB) OPERATION CHECK <Except vehicles without ABS>


caution A diagnosis code may be stored when carrying out the checks. Always erase the diagnosis codes after the checks, and then check that any diagnosis code is set.

POWER SUPPLY SYSTEM FUNCTION AND OPERATION CHECK
1.Turn the ignition switch to the LOCK (OFF) position. Depressurise the power supply system of the hydraulic brake booster (HBB) by depressing the brake pedal at least forty times until the pedal effort becomes high.
2.Check that the reservoir fluid level is at the MAX position.
3.Chock the wheels and release the parking brakes.
4.Turn the ignition switch ON, and measure how much time is elapsed after the pump motor starts until it stops.
Standard value: 20 - 80 seconds
5.After the pump motor stopped, start the engine. The brake warning lamp should not be turned on.
6.Stop the engine, and then turn on the ignition switch again.
7.When the brake pedal is depressed four or five times, the pump motor should start and then stop.
8.Depress the brake pedal four or five times again, and then measure how much time is elapsed after the pump motor starts until it stops.
9.Depress the brake pedal fully consecutive 15 - 20 times for ten seconds. The brake warning lamp should illuminate and the buzzer should sound.
Standard value: 2 - 11 seconds
caution Turn the ignition switch ON, and wait for at least 120 seconds before carrying out the checks.

SIMPLE INSPECTION OF HBB

  1. Turn the ignition switch to LOCK (OFF) position. Depressurise the power supply system of the hydraulic brake booster (HBB) by depressing the brake pedal at least forty times until the pedal effort becomes high.
  2. Depress the brake pedal, and turn the ignition switch ON. Then check the pedal. The pedal should be lowered. If no, the pedal is defective.

CHECK USING SIMPLE TESTER
1.Turn the ignition switch to the LOCK (OFF) position. Depressurise the power supply system of the hydraulic brake booster (HBB) by depressing the brake pedal at least forty times until the pedal effort becomes high.

2.Connect a pressure gauge and pedal effort gauge as shown, and bleed air from the pressure gauge.
3.Carry out the operation test without vacuum assist as follows:
(1) Turn the ignition switch to the LOCK (OFF) position. Depressurise the power supply system of the hydraulic brake booster (HBB) by depressing the brake pedal at least forty times until the pedal effort becomes high to observe the relationship between the pedal effort and the fluid pressure.
Standard value:
Pedal effort N
 Fluid pressure at front wheels MPa
 Fluid pressure at rear wheels MPa
100
 0.6 or more
 0
500
 4.5 or more
 0
4.Carry out the operation test with power assist as follows:
(1) Turn the ignition switch ON. Stop the pump motor, and then check the relationship between the pedal effort and the fluid pressure.
Standard value:
Pedal effort N
 Fluid pressure at front wheels MPa
 Fluid pressure at rear wheels MPa
100
 3.0 - 4.0
 3.3 - 4.3
200
 8.0 - 10.0
 8.0 - 10.0
400
 14.0 - 18.0
 14.0 - 18.0
500
 15.0 - 19.0
 15.0 - 19.0

BRAKE WARNING LAMP AND THE HBB BUZZER OPERATION CHECK
caution Turn the ignition switch ON, and wait for at least 120 seconds before carrying out the checks.


  1. Chock the wheels and start the engine.
  2. Release the parking brake lever, and depress the brake pedal fully consecutive 15 - 20 times for ten seconds. The brake warning lamp should illuminate and the buzzer should sound.