ABS Operation

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

During an ABS event, the ABS control module will control the hydraulic pressure in the individual wheel circuits to prevent any wheel from slipping. The control module can decrease or hold hydraulic pressure by energizing the appropriate valve solenoid. A rapid pulsation is felt in the brake pedal and a ticking or popping noise can be heard as control module commands valve solenoids in response to wheel speed changes.

When the ABS control module detects wheel slip, it holds pressure by closing both the inlet valve from the master cylinder and the outlet valve. If pressure hold is not enough to control wheel slip, the ABS control module releases pressure by opening the outlet valve and allowing some pressure bleed-off into the accumulator. The accumulator stores this fluid until the motor-driven pump returns fluid to the master cylinder.

The control module opens the inlet valve to allow master cylinder pressure to the wheel circuits again when no wheel slip is detected.