ABS System Components
The MK 25E Antilock Brake System (ABS) consists of a conventional hydraulic brake system plus antilock components. The conventional brake system includes a vacuum booster, master cylinder, front disc brakes, rear drum brakes, interconnecting hydraulic brake pipes and hoses, brake fluid level sensor and the brake warning lamp indicator.
The ABS components include a hydraulic unit, a Hydraulic Electronic Control Unit (HECU), system fuse, four wheel speed sensors (one at each wheel), interconnecting wiring, ABS indicator, the De-coupled Dynamic Rear Proportioning (DDRP) indicator (which is connected to the parking lamp) and the rear drum brakes.
The hydraulic unit with the attached Electronic Brake Control Module (EBCM) is located between the surge tank and the fire wall on the left side of the vehicle.
The basic hydraulic unit configuration consists of hydraulic check valves, two solenoid valves for each wheel, a hydraulic pump, two accumulators. The hydraulic unit controls hydraulic pressure to the front calipers and the rear wheel cylinders by modulating hydraulic pressure to prevent wheel lockup.