Antilock Brakes / Traction Control Systems: Description and Operation
Anti-Lock ControlBrake Fluid
WARNING: Use of any other than approved DOT 3 or DOT 4 brake fluid will cause permanent damage to brake components and will render the brakes inoperative.
WARNING: Brake fluid contains polyglycol ethers and polyglycols. Avoid contact with eyes. Wash hands thoroughly after handling. If brake fluid contacts eyes, flush eyes with running water for 15 minutes. Get medical attention if irritation persists. If taken internally, drink water and induce vomiting. Get medical attention immediately.
CAUTION: Brake fluid is harmful to painted or plastic surfaces. If brake fluid is spilled onto a painted or plastic surface, immediately wash it with water.
Use clean, fresh Ford High Performance DOT 3 Motor Vehicle Brake Fluid C6AZ-19542-AB or equivalent meeting Ford specification ESA-M6C25-A. If DOT 3 is not available, use Ford High Performance DOT 4 Brake Fluid or equivalent meeting Ford specification SAE J 1704.
^ Do not reuse brake fluid drained or bled from the system.
^ Do not use brake fluid that has been stored in an open container.
^ Do not use contaminated brake fluid.
Principles of Operations
Anti-Lock Control
The Anti-Lock-Brake System (ABS) control module receives wheel speed readings from each wheel speed sensor and processes this information to determine if an ABS event is necessary. The wheel speed sensor electrically senses each tooth of the wheel speed sensor indicators as it passes through the wheel speed sensor magnetic field.
The ABS control module continuously monitors and compares the rotational speed of each wheel and when it detects an impending wheel lock, modulates brake pressure to the appropriate brake caliper. This is accomplished by triggering the Hydraulic Control Unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS control module returns the solenoid valves to their normal position, and normal (base) braking resumes.
The hydraulic control unit has additional internal solenoid valves incorporated to enable control modulation of the wheel brake pressures.
The system works by transferring torque from the spinning wheel(s) to the wheel(s) with the most traction. This torque transfer is achieved by the hydraulic control unit applying the relevant brake(s).
The system is active at all road speeds. When the system is activated the driver is made aware of the fact by the illumination of a warning indicator "Braking Effort" located in the instrument cluster.
The ABS control module is self monitoring. When the ignition switch is turned to the RUN position, the ABS control module will do a preliminary electrical check, and at approximately 20 km/h (12 mph) the pump motor is turned on for approximately one half-second. Also, during all phases of operation the ABS control module (after the vehicle is in motion) checks for correct operation of the wheel speed sensors. Any malfunction of the ABS will cause the ABS to shut off. Normal power assisted braking, however, remains.
The ABS control module has the ability to store 16 DTCs in its memory.
The traction control system controls wheel spin by modulating the engine torque by communicating to the Powertrain Control Module (PCM) and by applying, then releasing, the appropriate brake to restore traction when one or both drive wheels lose traction and begin to spin during acceleration.
The traction control system can be disabled by pressing the traction control switch and is indicated by an LED in the traction control switch. The traction control will reset and return to normal traction assist when the ignition switch is cycled or when the traction control switch is pressed and released a second time.