Anti-lock Braking System Repair

Storefront of Hollenshades with Car Battery service

ABS / HCU Diagnosis and Repair

The anti-lock braking system on most vehicles is a four channel recirculating type system. The hydraulic control unit (HCU) of the system has one fluid channel for each wheel. The ABS control unit monitors wheel speed via speed sensors on each wheel. If lock-up is sensed at one or multiple wheel(s), the ABS Control unit will calculate the greatest amount of lock-up, then modulate wheel-speed by reducing brake fluid pressure at the locked wheel. This is accomplished by “dumping” brake line pressure inside the HCU.


If ABS system fault occurs, dash ABS light illuminates & brakes default to conventional operation. A diagnostic trouble code (DTC) will be stored into the system’s memory for diagnostics. Under most operating conditions, ABS brake control is not necessary and the brakes operate in a conventional manner.


ABS aids directional stability during heavy braking or slippery road conditions by allowing locked-up wheels to move. The ABS system shares the same brake fluid as the conventional system. This differs from older ABS system configurations that integrated two separate reservoirs, (one for ABS & one for the conventional brake system).


The experts at Hollenshade’s in Towson can address any problems you may experience with your vehicle’s brake system. Please CONTACT US for an appointment or to ask us a question about you brake calipers.

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