Brakes and Traction Control: Description and Operation

A four-wheel disc, computer controlled anti-lock brake system (ABS) is standard equipment.
The system uses four sensors (one at each wheel), which constantly send signals to the central microprocessor. The microprocessor then compares the rotational speed of all four wheels simultaneously. By comparing the rotational speed of all four wheels, the microprocessor can detect if one wheel begins to slow down more quickly than the others, indicating that lockup of that wheel may occur. If this is evident, it will command valves in the three hydraulic circuits (one for each front wheel, one for both rear wheels) to reduce and modulate line pressure, thereby preventing lockup from occurring. The ABS system is self-monitoring. If a malfunction of the anti-lock system should occur, normal braking operation is retained and the driver is alerted by both an instrument panel warning light and a message center warning. As part of the self-monitoring design, two microprocessors are used within the central unit. Each computer checks itself against the other, and against pre-programmed tests to ensure complete operational reliability. Power assist for the system is provided by an electric pump which charges a nitrogen filled accumulator upon demand.