Brief description, TC/ABS 5.3: Abs

The ABS is a control system that gives modern brake systems the ability to harness the maximum braking effect of the vehicle in critical situations, regardless of the road conditions.

The main advantages of the ABS system are:

• No loss of directional stability on braking.
• Steering control retained even during heavy braking.
• Shortest possible braking distance.
• Reduced tire wear.

The Saab 9-5 is equipped with TC/ABS 5.3, which is a dual-circuit, four-port brake system containing the following principal components:

• Wheel sensors, one at each wheel.
• TC/ABS hydraulic unit with the following integrated components:
  • Valve block with one inlet and one outlet valve per wheel for the ABS function.
  • One pressure increase and one pressure relief valve per front wheel for the TCS function.
  • Return pump consisting of an electric motor and pump unit, common to the ABS and TCS functions.
  • Control module with integrated main relay and pump relay. It controls both the ABS and TCS functions.

A wheel sensor at each wheel generates an alternating current with a frequency that increases as the speed increases. The TC/ABS control module, which receives the information on the wheel speed, calculates wheel acceleration (speed increase), wheel retardation (speed reduction), vehicle speed and wheel skid (degree of lock). If any of the wheels exceeds a certain degree of lock during breaking, the control unit will activate inlet and outlet valves and the return pump to regulate the wheel in question and attain maximum braking force with retained steering ability.

The control module incorporates a function known as electronic brake-force distribution (EBD), which controls the rear inlet valves so that maximum braking effect is achieved on the rear wheels under different load conditions, without the risk of their locking up before the front wheels.