ABS Description and Operation: Notes

This vehicle is equipped with the MK 25 E Continental Teves antilock braking system.

The vehicle is equipped with the following braking systems:

• Antilock Brake System (ABS)
• Engine Drag Control
• Electronic Brake Distribution
• Electronic Brake Control Module (EBCM)
• Hydraulic Brake Booster
• Traction Control System
• Vehicle Stability Enhancement System (with JL4)
• Optimized Hydraulic Braking System (with LNF)

The following components are involved in the operation of the above systems:

• Electronic Brake Control Module (EBCM)-The EBCM controls the system functions and detects failures.

  The EBCM contains the following components:

• Brake Pressure Modulator Valve (BPMV)-The brake pressure modulator valve contains the hydraulic valves and pump motor that are controlled electrically by the EBCM. The BPMV uses a 4 circuit configuration with a diagonal split. The brake pressure modulator valve directs fluid from the reservoir of the master cylinder to the left front and right rear wheels and fluid from the other reservoir to the right front and left rear wheels. The diagonal circuits are hydraulically isolated so that a leak or malfunction in one circuit will allow continued braking ability on the other.
  IMPORTANT: There is a rubber isolator located under the brake pressure modulator valve and on the mounting studs. The rubber isolators protect the brake pressure modulator valve and the EBCM from vehicle vibrations.

  The Brake Pressure Modulator Valve contains the following components:

  • Pump Motor
  • Inlet Valves (one per wheel)
  • Outlet Valves (one per wheel)
  • Master Cylinder Isolation Valves (one per drive wheel)
• Active wheel speed sensors (with LNF) - The EBCM sends a 12 V reference voltage to each wheel speed sensor. As the wheel spins, the wheel speed sensor sends a DC square wave signal. The EBCM uses the frequency of the square wave signal to calculate the wheel speed.
• Passive wheel speed sensors (without LNF) - As the wheel spins, a toothed ring located at each wheel hub interrupts a magnetic field in the wheel speed sensors. This causes the wheel speed sensors to generate an AC signal. The EBCM uses this AC signal to calculate the wheel speed. Any imperfections in the toothed ring, such as a missing or damaged tooth, can cause an inaccurate signal.
• Traction Control Switch - The TCS is manually disabled or enabled using the traction control switch.
• Brake Pedal Position - The EBCM uses the BPP sensor as an indication that the brake pedal is applied.
• Lateral Accelerometer Sensor (with JL4) - The EBCM uses the lateral accelerometer sensor as an indication of the lateral acceleration of the vehicle.
• Yaw Rate Sensor (with JL4) - The EBCM uses the yaw rate sensor as an indication of the yaw rate of the vehicle.
• Steering Wheel Position Sensor (with JL4) - The EBCM uses the steering wheel position sensor as an indication of the position and rotation of the steering wheel.