Isuzu KB P190. Manual - part 150

BRAKE CONTROL SYSTEM   5A-7 

Normal Braking 

During normal (non anti-lock) braking, the solenoid 
valve has current flow. 

 

Brake fluid travels through the center of the inlet valve 
around the outlet valve then to the brake pistons. 

 

 

RTW75AMF000201 

Legend 

(1)  Master Cylinder  

(5) Brake 

(2) Brake 

Pedal 

(6) Outlet Valve 

(3)  Motor and Pump 

(7) Inlet Valve 

(4) Accumulator 

 

 

 

5A-8   BRAKE CONTROL SYSTEM 

Pressure Isolation (Pressure Maintain) 

The electronic-hydraulic control unit is activated when 
the brakes are applied. 

If the information from the wheel speed sensors 
indicates excessive wheel deceleration (imminent 
lockup), the first step in the anti-lock sequence is to 
isolate the brake pressure being applied by the brake 
pedal. 

 

The microprocessor in the Control Unit sends a voltage 
to the coil to energize and close the outlet valve. This 
prevents any additional fluid pressure applied by the 
brake pedal from reaching the wheel. With the outlet 
valves closed, unnecessary increase in the brake 
pressure is prevented. 

 

 

RTW75AMF000301 

Legend 

(1)  Master Cylinder  

(5) Brake 

(2) Brake 

Pedal 

(6) Outlet Valve 

(3)  Motor and Pump 

(7) Inlet Valve 

(4) Accumulator 

 

 

 

BRAKE CONTROL SYSTEM   5A-9 

Pressure Reduction 

Once the brake pressure is isolated, it must be reduced 
to allow the wheels to unlock. This is accomplished by 
dumping a portion of the brake fluid pressure into the 
accumulator. 

The microprocessor activates the normally closed outlet
valve to open, allowing fluid from the wheels to be 
dumped into the accumulator. This is done with very 
short activation pulses opening and closing the outlet 

 

valve passageway. Brake pressure is reduced at the 
wheel and allows the wheel to begin rotating again. The 
fluid from the brake piston is stored in the accumulator 
against spring pressure and a portion of this fluid also 
primes the pump. 

The outlet valves are operated independently to control 
the deceleration of the wheel. 

 

 

RTW75AMF000401 

Legend 

(1)  Master Cylinder  

(5) Brake 

(2) Brake 

Pedal 

(6) Outlet Valve 

(3)  Motor and Pump 

(7) Inlet Valve 

(4) Accumulator 

 

 

 

5A-10   BRAKE CONTROL SYSTEM 

Brake Release 

At the end of the anti-lock stop, when the brake pedal is 
released, the pump will remain running for a short time 
to help drain any fluid from the accumulator. As this fluid 
returns into the system, the spring forces the piston  

 

back to its original position. 

The inlet valve opens and fluid may return to the master 
cylinder. Conventional braking is then resumed. 

 

 

RTW75AMF000501 

Legend 

(1)  Master Cylinder  

(5) Brake 

(2) Brake 

Pedal 

(6) Outlet Valve 

(3)  Motor and Pump 

(7) Inlet Valve 

(4) Accumulator