The Electro-Hydraulic Control Unit (EHCU) consists of the Electronic Brake Control Module (EBCM) and the Brake Pressure Modulator Valve (BPMV). The EHCU regulates hydraulic pressure in the brake system during an ABS event.

The Electronic Brake Control Module (EBCM) is the electronic portion of the EHCU assembly. The EBCM receives and processes numerous sensor and switch inputs and then controls BPMV function if it is necessary to respond to these inputs. Inputs to the EBCM include the following:

The EBCM can command the following outputs:

The Brake Pressure Modulator Valve (BPMV) is the hydraulic/mechanical portion of the EHCU, consisting of a valve body and pump motor. The BPMV is actuated by the EBCM in order to regulate hydraulic pressure in the following brake circuits:

Each circuit within the BPMV has an isolation valve and a dump valve. These valves are used to hold, decrease or increase hydraulic pressure within the brake circuits. There are 2 low pressure accumulators located within the BPMV, which are used to store brake fluid in the unit during ABS operation. The pump, also located within the BPMV, is used to return fluid from the accumulators to the master cylinder or fluid reservoir.

The front Wheel Speed Sensors (WSS) are a magnetic coil/pickup type. Each WSS produces an AC voltage signal which is received by the EBCM. The AC voltage is produced as the teeth on a toothed ring pass through the magnetic field of the WSS pole piece. The frequency of the AC signal is used to calculate the wheel speed. Any imperfections in the toothed ring, such as a missing or otherwise damaged tooth, can cause an inaccurate wheel speed sensor signal.

The rear wheel speed input signal originates at the vehicle speed sensor (VSS) and is supplied to the EBCM by the Vehicle Conrol Module (VCM) or Powertrain Control Module (PCM).