Mazda 323/MX-3/626/MX-6/Millenia/Protégé 1990-1998 and Ford Probe 1993-1997

General Description


Anti-lock braking systems are designed to prevent locked-wheel skidding during hard braking or during braking on slippery surfaces. The front wheels of a vehicle cannot apply steering force if they are locked and sliding; the vehicle will continue in its previous direction of travel. The four wheel anti-lock brake systems found on Mazda vehicles holds the individual wheels just below the point of locking, which in turn allows some steering response and prevents the rear of the vehicle from sliding sideways.

Electrical signals are sent from the wheel speed sensors to the ABS control unit; when the system detects impending lock-up at any wheel, solenoid valves within the hydraulic unit cycle to control the line pressure as needed. The systems employ normal master cylinder and vacuum booster arrangements; no hydraulic accumulator is used, nor is any high pressure fluid stored within the system. The system employs a conventional master cylinder and vacuum booster arrangements; no hydraulic accumulator is used, nor is any high pressure fluid stored within the system.


The ABS system monitors and compares wheel speed based on the inputs from the wheel speed sensors. The brake pressure is controlled according to the impending lock-up computations of the ABS control unit.

If either front wheel approaches lock-up, the controller actuates the individual solenoid for that wheel, reducing pressure in the line. Impending lock-up at either rear wheel will engage the rear control solenoid; hydraulic pressure is reduced equally to both rear wheels, reducing the tendency of the rear to skid sideways under braking.


Certain components within the ABS system are not intended to be serviced or repaired individually. Only those components with removal and installation procedures should be serviced.
Do not use rubber hoses or other parts not specifically specified for the ABS system. When using repair kits, replace all parts included in the kit. Partial or incorrect repair may lead to functional problems and require the replacement of components.
Lubricate rubber parts with clean, fresh brake fluid to ease assembly. Do not use lubricated shop air to clean parts; damage to rubber components may result.
Use only DOT 3 brake fluid from an unopened container.
If any hydraulic component or line is removed or replaced, it may be necessary to bleed the entire system.
A clean repair area is essential. Always clean the reservoir and cap thoroughly before removing the cap. The slightest amount of dirt in the fluid may plug an orifice and impair the system function. Perform repairs after components have been thoroughly cleaned; use only denatured alcohol to clean components. Do not allow ABS components to come into contact with any substance containing mineral oil; this includes used shop rags.
The Anti-Lock control unit is a microprocessor similar to other computer units in the vehicle. Ensure that the ignition switch is OFF before removing or installing controller harnesses. Avoid static electricity discharge at or near the controller.
If any arc welding is to be done on the vehicle, the ALCU connectors should be disconnected before welding operations begin.