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Home >> Volvo >> 2008 >> XC70 >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Electrical Modules And Components - Design And Function - 1 Of 5 >> Brake Control Module (BCM) (2008-2012) >> Function >> EBD Function
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EBD Function

Fig 1: Identifying EBD Function
GLL106635Courtesy of VOLVO CARS CORPORATION

The EBD function is integrated with the ABS system and regulates brake force to the rear wheel brakes. EBD control regulates the hydraulic pressure in the rear wheel brake circuits so that the rear wheels spin slightly less than the front wheels during braking. This enables the vehicle to decelerate in an optimal, stable manner.

The brake control module (BCM) regulates brake pressure by controlling the intake and outlet valves in the rear wheels' brake circuit.

Brake pressure in the rear wheel circuit is regulated differently depending on how much the rear wheels are spinning in relation to the front wheels. Control strives to keep rear wheel spin 0-2% less than front wheel spin. The function can thus be said to be load detecting.

In general, the difference in spin between the rear wheels and front wheels during braking is greatly dependent on the severity of the braking and how heavily the vehicle is loaded. Hard braking/light load can generate more spin; light braking/large load can generate less spin.

Because EBD control requires less brake fluid than during stability and traction control, the hydraulic pump is not activated. The volume of fluid returned from the brake circuits is collected by the accumulators.