ABS Solenoid Valves

Using the picture as a guide, which of the following gives the correct condition of the inlet and outlet solenoid valves under normal braking?

A: Inlet Valve Open Outlet Valve Open

B: Inlet Valve Open Outlet Valve Closed

C: Inlet Valve Closed Outlet Valve Open

D: Inlet Valve Closed Outlet Valve Closed

Answer = B.

When the brakes are being used normally and there is no ABS action required, the inlet valves are held open, and the outlet valves are held closed.


Which of the following gives the correct condition of the inlet and outlet solenoid valves when the ABS is operating to reduce wheel back pressure?


A: Inlet Valve Open Outlet Valve Open


B: Inlet Valve Open Outlet Valve Closed


C: Inlet Valve Closed Outlet Valve Open


D: Inlet Valve Closed Outlet Valve Closed


Answer = C
When the ECU detects that the pressure at a wheel needs to be reduced to prevent skidding the outlet valve is opened by a signal from the ECU.


Which of the following gives the correct condition of the inlet and outlet solenoid valves when the ABS is operating to hold back pressure?


A: Inlet Valve Open Outlet Valve Open


B: Inlet Valve Open Outlet Valve Closed


C: Inlet Valve Closed Outlet Valve Open


D: Inlet Valve Closed Outlet Valve Closed


Answer = D
When the ECU detects the sudden decceleration of a wheel, indicating the wheel is about to skid, it signals the hydraulic control unit to hold the pressure at that brake. The outlet valve is already closed and the signal from the ECU closes the inlet valve.


Which of the following gives the correct condition of the inlet and outlet solenoid valves when the ABS is operating to increase wheel back pressure?


A: Inlet Valve Open Outlet Valve Open


B: Inlet Valve Open Outlet Valve Closed


C: Inlet Valve Closed Outlet Valve Open


D: Inlet Valve Closed Outlet Valve Closed


Answer = A


After the pressure at the wheel has been reduced and the wheel is no longer about to skid, the pressure can be increased: The outlet valve is closed so that fluid cannot pass to the accumulator and pump. The inlet valve is opened so that pressure can be increased.



In the four cases above state when the ABS motor will be working?


When the ABS is opening solenoid valves and trying to reduce pressure