Vehicle Response In Anti-Lock Mode

RESPONSE
During anti-lock braking, the anti-lock Electronic Control Unit (ECU) cycles the modulator solenoid valves rapidly. As the solenoids in each channel isolate, build, decay pressure as needed, the driver may experience a pulsing sensation in the vehicle. This sensation occurs as the individual brake units apply/release during anti-lock braking. Pulsing is a result of normal front-to-rear and side-to-side pressure modulation and is considered normal.

With most failure conditions, the brake pressure modulation is deactivated and the system reverts to "baseline" braking capabilities. If the fault occurs during cycling, the build and isolation valves are held open momentarily in most cases, allowing the boost source to rebuild pressure in the system in order to minimize pedal drop. With some failures such as low voltage or lost boost pressure, the delayed shutdown sequence is not practical and the master cylinder will provide any rebuild pressure, resulting in pedal drop. Extra stroke has been included in the master cylinder to provide some reserve displacement for this condition.